Henry James was in his late 30s when he published his first uncontested masterpiece, “The Portrait of a Lady” (1880-81), which elevated him from a talented up-and-comer to a major novelist. It is the story of an intelligent, independent young woman named Isabel Archer who is taken from America to England and allowed to make something of herself, but who “affronts” her destiny (as James worded it) by making a bad marriage. When James revised the novel for the collected New York Edition of 1908, he wrote a preface to account for its origins and aims, concluding after a dozen pages with the admission, “There is really too much to say.”

That’s where Michael Gorra steps in with “Portrait of a Novel,” devoting more than 300 intelligent pages to everything James left unsaid about this superb, game-changing book.

Mixing literary criticism with biography and travelogue, Gorra — an English professor at Smith College — provides a fascinating “making of” documentary like those that accompany some films these days. Literally following in James’s footsteps — Gorra visited the places in Italy and England where James composed the novel — he alternates between close readings of the novel itself and wide-ranging background material drawn from James’s life and writings. To some extent, he imitates the form of James’s novel, which moves crab-wise both forward and sideways as James frequently interrupts the linear story line to backtrack or leap forward over events (such as the first few years of Isabel’s marriage) or to bring it to a halt for a dozen pages while Isabel simply thinks. Gorra even weaves unattributed quotations from James’s writings into his own exquisite prose, giving his “Portrait” the same varnished finish as James’s “Portrait.”

Gorra demonstrates that James was interested less in plot than in character, and specifically in consciousness. “The novel isn’t finally about a young woman’s choice of a husband, or even about Americans in Europe,” Gorra writes. “It is instead a drama of the perceiving mind.” James hoped this sort of intellectual drama would be as “interesting,” he wrote in his 1908 preface, “as the surprise of a caravan or the identification of a pirate,” the stuff of commercial fiction. Gorra underlines how radically James broke from the fiction practices of the 19th century in this novel. Not only did he shift the emphasis from plot to character, but he introduced into fiction one of the earliest examples of “stream of consciousness” (his older brother William’s phrase), and he dared to leave his ending unresolved, to the frustration of many readers.

James was one of the first purveyors of what is now maligned as “difficult” fiction, especially in his later novels when he stopped writing to please his audience. “He writes now as if he wants only to please himself,” Gorra remarks of this final phase, “and to the degree that he’s concerned with his readers at all, it’s to pay the fit and the few the compliment of assuming that they’ll be able to follow.”

”Portrait of a Novel: Henry James and the Making of an American Masterpiece” by Michael Gorra. (Liveright)

This is an attitude associated with Joyce and his postmodern progeny, but Gorra persuasively argues that such challenging fiction began with James’s “Portrait.” The Anglo-American novelist agreed with the French novelists he knew that it was time to write for mature adults; the “English system was good for virgins and boys, and a bad thing for the novel itself,”James wrote in a review of Zola’s “Nana,” a novel then inconceivable and unpublishable in England or America. For the French, writing for adults meant dealing with squalor and sexuality, but for James it meant converting the novel from entertainment to art, a classification few people were willing to grant it, even at that late stage in literary history. Hemingway famously said all modern American fiction came from “Huckleberry Finn,” which may be true of relatively undemanding fiction such as his; but the more demanding work of Faulkner, Gaddis, Pynchon, David Foster Wallace and others (Gorra implies) comes from “The Portrait of a Lady.”

Much contemporary literary criticism is so arcane as to be almost incomprehensible, but Gorra’s book reads beautifully, closer to belles lettres than to academic criticism. He identifies the real-life originals behind James’s characters and places, but steers us to the proper use of this information: “Searching for some putative original allows us to see what was in fact created; the difference between the fictional page and the gravel of documentary truth can stand as a guide to artistic practice.” There is more biographical information here than in most monographs on individual novels, but the emphasis is always on how James shaped that material to aesthetic ends.

Gorra’s “Portrait of a Novel” is a model for the once-discredited biographical approach to criticism, a demonstration of how richly rewarding such an approach can be in the right hands. It is an important book not only for James enthusiasts, but for anyone interested in what Gorra christens “the bridge across which Victorian fiction stepped over into modernism.”

Moore is a literary critic; the second volume of his study “The Novel: An Alternative History” will be published next year.