The sheer size of “The Novel” (Princeton University Press, $99.50 per volume), a new two-volume compendium of scholarly essays on every aspect of the history and nature of the genre, makes a sort of claim. Clearly, a literary form that requires some 1,700 pages of examination must be inherently problematic: Its origins, its techniques, its effects on readers must cry out for expert investigation. Yet the claim posed by “The Novel” (and still more by its original Italian version, Il romanzo, which is twice as long), seems counter-intuitive, given how central novels and fiction are to our current understanding of literature. In any bookstore, the sum total of all printed matter is divided into two categories, fiction and everything else. The novel, you might say, is like pornography: It may be hard to define, but everyone knows it when they see it.

Yet it is exactly the cultural phenomena that are most obvious, that surround us as invisibly as an atmosphere, that most need questioning.Take a seemingly simple question that arises again and again in “The Novel”: What was the first novel? Among English readers, there are a few standard answers: Samuel Richardson’s “Pamela,” the epistolary novel that appeared in 1740, or Daniel Defoe’s “Robinson Crusoe,” which was advertised as a true story when it was published in 1719. Widen the focus to Western Europe, however, and Defoe looks like a latecomer compared to the French women novelists of the 17th century, notably Madame de Lafayette (author of the courtly novel “La Princesse de Cleves”) and Madame de Scudery. And even before the courtiers of the Sun King devoured those amorous tales, there was “Don Quixote,” published in 1605 and often baptized as the first novel, though it reads very unlike the novels we know today.

Yet “Don Quixote” itself vanishes in an abyss of precursors. What about the prose romances of the Renaissance, or the novelle of Boccaccio and the tales of Chaucer, popular in the 14th century? Or the chivalric verse romances of the Middle Ages, which grew to encompass dozens of episodes? Or the Greek novels of the Hellenistic period, like Heliodorus’s “Aethopika,” with their tales of lovers reunited after fabulous ordeals? For that matter, isn’t the “Odyssey” itself essentially novelistic, with its focus on domestic relationships and psychological predicaments?

When you open “The Novel,” in other words, you may think you know what a novel is; by the time you close it (not to say finish it, since few nonprofessionals will read it from beginning to end), you are no longer sure. And if there is one goal that all the diverse contributors to “The Novel” share, it is this sort of estrangement. Under the editorship of Franco Moretti, an Italian who teaches at Stanford and is one of the most unorthodox and influential scholars of the novel today, dozens of academics from around the world have contributed studies in their areas of expertise.

Their essays are grouped under broad rubrics. The first volume, subtitled “History, Geography and Culture,” has sections such as “Polygenesis,” on the multiple origins of the novel, and “Toward World Literature,” on the way the genre has been adapted in Africa and Asia. The second volume, devoted to “Forms and Themes,” is more literary-critical (at times drearily so),organized around themes like “Writing Prose” and “Space and Story.” The result is not an encyclopedia but a potpourri — a loosely structured work that does not define the novel so much as it illustrates the way today’s scholars think about it.

The sheer diversity of topics here is exciting and opens up many new horizons. Henry Y.H. Zhao, writing on “Historiography and Fiction in Chinese Culture,” shows how the term xiaoshuo, defined in the first century A.D. as mere “gossip and hearsay,” the lowest form of writing, emerged as the modern Chinese term for literary fiction. Catherine Gallagher, in one of the collection’s best essays, discusses “The Rise of Fictionality,” showing how the 18th-century European novel helped to create the notion of stories that can freely explore reality because they do not claim to be real: “a nonreferentiality,”as she puts it, “which could be seen as a greater referentiality.” Another excellent contribution is Bruce Robbins’s “A Portrait of the Artist as a Social Climber,” which explores the paradoxical, subtly hypocritical figure of the bohemian — the artist who turns his material deprivation into a badge of spiritual aristocracy.

Beyond these fairly conventional historical essays, “The Novel” also makes room for some more eccentric approaches.The French scholar Nathalie Ferrand writes about SATOR, the Society for the Analysis of Novelistic Topoi, which has worked over the last two decades to compile a computer database of every plot element used in 18th-century French fiction.This goal remains as elusive as Casaubon’s “Key to All Mythologies”in “Middlemarch”— even Ms. Ferrand calls it “a rather mad idea” — but it stimulates some interesting debates about how to analyze fiction. Likewise, Espen Aarseth’s essay on “Narrative Literature in the Turing Universe”explores the netherworld of Dungeons and Dragons and online role-playing games, reaching the sane conclusion that gamelike simulations have little in common with novelistic narrative.

But the most enticing parts of “The Novel” are the sections of “readings,” focused on individual novels grouped around a theme: novels of the metropolis, political novels, novels of the Americas.When it comes to these brief sketches, the less familiar the subject, the better. An American reader will probably yawn at yet another summary of “Huckleberry Finn.” But other readings will send him straight to the library, eager to find Recaizade Mahmut Ekrem’s “A Carriage Affair,” a Turkish novel of 1896, about a young man’s incompetent pursuit of a courtesan; or Mao Dun’s “Midnight,” published in China in 1932, with its lurid portrait of pre-Communist Shanghai; or “Love in Excess,” the 1719 novel of sex and sentiment by Eliza Haywood, who was once as famous as Defoe or Richardson. Such essays are a reminder that the canon of Western fiction, though large enough for a lifetime’s reading, is still just one galaxy in the universe of the novel.

A universe, by definition, can’t be summarized, and neither can “The Novel.” Contributors are given their freedom, not just to range widely, but to disagree fervently on basic issues.Take that vexed question of the novel’s origins. Different contributors trace its parentage to ancient Greek tales, Chinese historiography, Indian epic, and even rabbinical midrash. But the preponderance of the evidence suggests that the conventional wisdom is correct. It is impossible to understand why the novel has been the quintessential modern art form, and why it has appealed to writers and readers around the globe, without understanding the circumst ances of its rise in Western Europe in the 18th century.

The most important factor in that rise was that the novel began life as a defiantly low, critically stigmatized genre. It was the first literary form to be written and read largely by women; to seek a popular, democratic audience; and to consider realism a virtue instead of a low vice. In all these ways, it helped to incarnate the modern sensibility, and to teach its readers what it means to be modern. It is the novel, as opposed to earlier forms of narrative, that made the ordinary mind’s encounter with the ordinary world a source of drama and significance. If the novel is indeed losing its central position in our imaginative life — and while “The Novel” seldom addresses this possibility, its very comprehensiveness can suggest an autopsy report — it can only be because modernity itself is slipping away, with all its distinctive promise and menace. The dispensation that replaces modernity may be better or worse, but if it does not see its own reflection in the novel, it cannot help appearing to us as somehow less human.

akirsch@nysun.com