C.S. Lewis’ allegory opens with the narrator, presumably a middle-aged Englishman, walking through the rainy streets of a city at dusk. He happens upon a line of bickering people waiting for a bus and, almost by accident, he’s in the queue, and then aboard the bus, not knowing where it’s bound.

As the bus ascends, he gets a broad view of his vast, gloomy country, with its houses spread miles apart as its inhabitants try to distance themselves ever further from their neighbors.

The bus eventually rises to a lush, sunlit country in which the substance of all things, from the grass to the water to the animals, is so hard and weighty that the passengers on the bus are mere ghosts by comparison.

Bright spirits approach the passengers one by one, each assigned to a specific individual, and try to convince the ghosts to accompany them on the difficult journey over the mountains to a land of joy and love. The one condition is that they can’t take anything with them.

One by one, the ghosts refuse. The proud ones cannot give up their important roles in the world below. The wounded and the wronged cling to their wounds as an identity that defines their entire being. The ones who exercised power refuse to go forward without the guarantee that their power will be preserved or restored.

The bright spirits cannot give the ghosts a sense of the joy that awaits them because the ghosts are so attached to their own misery that they can’t conceive of joy. Unaware of the limits of their understanding, the ghosts cling to their identities as a last possession, and fear that once they’re stripped of that, they’ll become nothing.

The spirits argue, to no avail, that once the ghosts relinquish those last vestiges of self, they actually become more substantial, and the journey over the mountains becomes easier, though they acknowledge that the beginning of the journey is always painful, in different ways for different people. One ghost, a woman who was admired and beautiful in the world below, cannot bear the shame of being transparent, of being “seen through” in this new world. The spirit explains that surrendering to her shame is the first step toward becoming a more substantial being.

“Don’t you remember on earth–there were things too hot to touch with your finger but you could drink them all right? Shame is like that. If you will accept it–if you will drink the cup to the bottom–you will find it very nourishing: but try to do anything else with it and it scalds.”

The ghosts are more interested in complaining about their place in the world below than in listening to what awaits in the world above. One of Spirits, offering joy and freedom to an unreceptive ghost, expresses his frustration: “Friend,” said the Spirit, “Could you, only for a moment, fix your mind on something not yourself?”

The story is in some ways like an abridged and inverted version of Dante’s Inferno. The setting is heaven instead of hell, and instead of seeing the punishment inflicted on the damned, we see the mindsets and attitudes that lead to their misery. None of these ghosts did anything particularly horrible. They look like our neighbors, our families, and ourselves. They’re manipulative or sulking or spiteful or proud. They’re selfish and inflexible. They lack empathy. They’re full of petty grievances, and their smothering “love” for others is merely a desire to possess and control.

Many of them sunk unwittingly into misery, like the grumbling old woman, whose downward trajectory through life is described thus:

“…it begins with a grumbling mood, and yourself still distinct from it: perhaps criticizing it. And yourself, in a dark hour, may will that mood, embrace it. Ye can repent and come out of it again. But there may come a day when you can do that no longer. Then there will be no you left to criticize the mood, nor even to enjoy it, but just the grumble itself going on forever.”

Others have followed a similar descent, so slow and subtle they can’t recognize their own misery. One of the Spirits describes an example:

“The sensualist, I’ll allow ye, begins by pursuing a real pleasure, though a small one… But the time comes on when, though the pleasure becomes less and less and the craving fiercer and fiercer, and though he knows that joy can never come that way, yet he prefers to joy the mere fondling of unappeasable lust and would not have it taken from him.”

The narrator watches as, one by one, the ghosts refuse the offer of joy and board the bus back to hell. And here again Lewis inverts Dante. In The Inferno, the souls know they’re suffering, their suffering is inflicted from without by a being substantially greater than them (the devil) against whom they are powerless. Hell has no exit, and their suffering is eternal.

In The Great Divorce, the inhabitants of the underworld are free to go anytime. They can and do board that bus to heaven, but they choose again and again to return to gloomy world below, to the role and the self and the life they’ve so identified with that they cannot let it go. Their hardships and troubles are self-inflicted, and they don’t know they’re suffering.

“There is always something they insist on keeping even at the price of misery,” one of the Spirits remarks. “There is always something they prefer to joy.”

Unlike the exotic world of extreme torture that Dante paints, Lewis’ hell looks a lot like the world we live in now.

The Bestseller Code, by Jodie Archer and Matthew L. Jockers, describes the results of a five year computer analysis of over 20,000 novels. The authors wanted to figure out what differentiates the 500 or so New York Times bestsellers in their corpus from the rest of the titles that didn’t make the bestseller list.

The subtitle, Anatomy of a Blockbuster Novel, describes the book’s goal, which is to describe the common traits of bestsellers, revealing some hidden and unexpected characteristics along the way.  The book does not pretend to offer a formula for writing bestsellers. A similar book in the world of sports might reveal insights into what made Michael Jordan, Kobe Bryant, and LeBron James such great basketball players, but that doesn’t mean you or I could follow the formula and become the next NBA superstar. This book is a descriptive anatomy, not prescriptive how-to.

The authors use highly-customized Natural Language Processing (NLP) software to analyze thousands of data points within each book, including the frequency of different words and word types, sentence length, which topics appear and with what frequency, and where the emotional high and low points of the plot occur.

One thing you should know about NLP software is that it enables the computer to describe a text, but it does not enable the machine to understand the text. For example, in reading Harry Potter, NLP software will point out that virtually every paragraph that mentions Voldemort is full of words that express negative sentiment (words like evil, terrible, fearful, etc.). From this, the software can infer that Voldemort is the villain. However, NLP software does not understand what it reads the way a human does. It cannot answer complex questions like, “How does Mrs. de Winter’s understanding of her world change when Maxim says, I never loved her?”

Most of Archer and Jockers’ findings make perfect sense, and will be familiar to people who read a lot of novels and to those who read the advice of successful authors on the craft of writing. Readers prefer an active protagonist to a passive one. Readers prefer language that’s close to the everyday vernacular over the more formal type of writing that appears in essays. Bestselling authors do not overload their sentences with adjectives and adverbs. They convey meaning with nouns and verbs, which makes the reading experience smoother and more fluid.

Bestsellers tend to focus on a few topics within each work, rather than trying to hit on every theme the author can think of. Typically, the three major topics of a bestseller account for about 30-40 percent of the total topical matter of the work. Certain topics are more likely to make a bestseller: technology, work, family life, close interpersonal relationships. Surprisingly, sex is not one of those topics, and bestsellers in general tend to feature less sex than non-bestsellers.

Archer and Jockers identify seven structural patterns common to the plots of all bestsellers. They present the structural patterns as line graphs, which give a clear picture of the story’s emotional highs and lows. The summary of the classic love story, for example, is “Boy meets girl, boy loses girl, boy gets girl back.” If you were to draw that as a line graph, there would be a high point near the beginning when the boy first meets the girl, followed by a low point in the middle when he loses her, and another high point at the end, when he gets her back.

One of the book’s surprising findings is that the emotional curves of all bestsellers follow one of these seven graphs. The plot lines hold for trashy romances, far-fetched thrillers, and revered literary prizewinners. The Bestseller Code even charts the plots of some of these seemingly disparate novels together on the same graph to show you how similar they are.

Much of the value of this book comes from its clear and well-described insights into what readers respond to, and from the authors diving into a number of texts to provide illuminating examples of the generalized patterns that the computer has revealed. Jockers has more of a traditional English-lit background, and will occasionally touch on books by Virginia Woolfe and James Joyce. Archer comes from the publishing world, and her discussions focus on more current works.

One work they dig into is the unexpected phenomenon Fifty Shades of Grey, which, on its surface, seems to defy all the rules. It was written by an indie author with no marketing to propel it, one of its primary topics is sex (and not mainstream vanilla sex, but BDSM) which is not part of the “bestseller DNA”, and both readers and critics mocked the quality and style of its writing. But for all that, it sold hundreds of millions of copies. Why?

This is where the computer analysis really shines, as it points out characteristic patterns of the work without the baggage of emotional or aesthetic judgement that a human reader would bring. The analysis showed that E.L James, despite what some might call a lack of style, had hit on every element of the blockbuster novel, from topical makeup to plot structure to character. The analysis also showed that, based on the number of paragraphs devoted to each topic, the book was more about close interpersonal relationships than sex in general. And “close personal relationships,” the authors remind us, is one of the top themes common to all bestsellers.

While the overall public discussion of Fifty Shades tended to focus more on the sex, the computer was able to see that readers were experiencing, perhaps on a less unconscious level, the same sorts of interpersonal relations that fascinate them in the genres of mystery, thriller, and historical drama.

Even more interesting, Archer and Jockers point out, is the plot structure of Fifty Shades, which is a subtle and unusual variation of one of the six basic structures common to all bestsellers. James’ novel, generally follows “Plotline 4,” which Christopher Booker, in The Seven Basic Plots, calls “Rebirth.” Archer and Jockers point out that “these plots tend to see the main characters experience change, renewal, and some sort of transformation.”

The twist that James put on this basic plot is that, instead of following the plot’s typical emotional pattern of beginning-high-low-high-low-end, she created a series of highs and lows throughout the book, which occurred at such regular intervals that the graph of them looks almost like a perfect sine wave. Archer and Jockers refer to this pattern as the emotional rhythm of the plot.

Outside of the Harry Potter series, which was primarily aimed at young readers, the only “adult” book in the past twenty years whose sales numbers compare to Fifty Shades is Dan Brown’s The Da Vinci Code. The authors point out that although The Da Vinci Code’s basic plot differs from Fifty Shades, the two books share an almost identical emotional rhythm. Page 106 of The Bestseller Code shows a graph of the two plot lines, with the high points, low points, and inflections points of both novels appearing almost in lockstep. Now who would have thought to compare those two books, or even mention them in the same breath?

Both were runaway bestsellers, and on an emotional level, both provided a strikingly similar reading experience despite their differences in topic, style, tone, and genre. That insight about emotional experience reminded me of a question and answer I read recently on Quora. A reader asked why the Harry Potter series was so popular despite the fact that its plots were not necessarily new and other writers had more interesting styles and were better at world building. An author named Nick Travers offered this response:

I used to think the same as you. I even thought, ‘I can write as well as that,’ so I started to write a novel to prove it.

Four novels later and I can write as well as J.K.Rowling, but the quality of my stories pale into insignificance compared to hers. What I’ve learned is that J.K. Rowling is not a particularly good writer, but she is a master story teller. When she tells a story it sparkles with magic in a way that draws people (especially youngsters) into her world. I wish I could tell stories like that.

The Bestseller Code maps out some of the characteristics and common traits of great story-telling in illuminating ways, and the authors’ commentary on a diverse body of well-known works makes it a fun and interesting read. If you’re interested in understanding what drives readers to buy books, this one is worth a read.