A year after his death on Jan. 27, 2010, it’s tough to know how to assess J.D. Salinger; there are too many loose ends.

How can we miss a writer who removed himself from the public conversation nearly half a century before he died?

At the same time, nothing in the last 12 months has suggested any loosening of the grip he maintained on his writing while he was alive. Whatever Salinger may have produced since his last published piece — the novella “Hapworth 16, 1924” appeared in the New Yorker in 1965 — remains out of reach.

So while Kenneth Slawenski’s “J.D. Salinger: A Life” is the first comprehensive biography of the reclusive author, it does little to resolve the issue of Salinger’s legacy. Instead, it is more an extended letter from a fan. Since 2004, Slawenski has been the proprietor of DeadCaulfields.com, a website devoted to all things Salinger, and he’s been working on this project for longer than that. Originally published last March in England under the title “J.D. Salinger: A Life Raised High,” his is a book that blends workmanlike doggedness with a fair amount of critical overstatement while still managing to frame its subject’s life.

Yet it’s less the details of his life than the content of his work that defines Salinger’s significance. “The Catcher in the Rye,” “Nine Stories,” “Franny and Zooey,” “Raise High the Roof Beam, Carpenters and Seymour — An Introduction”: Here we have the enigmatic substance of his legend, through which readers have long refracted their own alienation and desires.

At the heart of Slawenski’s portrayal is his account of Salinger’s experiences during World War II, when, in less than 11 months, he participated in the invasion of Normandy, helped liberate Paris and — if Slawenski has conjectured correctly — ended up confronting the human wreckage at Dachau, where the “stench, according to eyewitness, could be smelled 10 miles away.” The key concept here is conjecture, for as Slawenski admits, “(l)ike so many who encountered such scenes during the war, Salinger has never spoken directly of his experiences, and we cannot be certain of exactly what his … duties demanded of him.” Nonetheless, because a division to which he was attached was later recognized “as a liberating unit of Nazi concentration camps,” Slawenski concludes “it is evident that J.D. Salinger was called upon to take part in the liberation of victims of the Dachau concentration camp.”

Such a passage neatly encapsulates both the challenges and the difficulties of this book: that too much remains unknown. It’s not just the war years, which clearly scarred the author; in July 1945, still in Germany, he checked himself into an Army hospital for treatment of what was probably post-traumatic stress disorder. Indeed, it’s no stretch to suggest, as Slawenski does, that Salinger’s time in battle rendered him fatalistic and had a lot to do with the direction of his later work.

And yet, because Salinger was so guarded — destroying correspondence, eschewing interviews, compelling friends to silence — Slawenski has to depend throughout the book on many secondary sources, including the author’s writings, to fuel his conjectural leaps. He culls from archives at Princeton and the University of Texas, among other places, where some of Salinger’s papers are kept. “It is probably dangerous to read its characters as autobiographical,” he writes of an unpublished early story called “Birthday Boy,” but again and again he has no choice but to offer precisely these sorts of readings, equating Salinger, at various points, with both Seymour and Buddy Glass as well as Holden Caulfield, looking for the correlations between his fiction and his inner self.

This is a double-edged sword, especially for readers familiar with Salinger’s work. Slawenski’s analyses are often inconsistent, if not incorrect. Discussing school-board challenges to “The Catcher in the Rye,” he oddly wonders at Salinger’s silence, then cites a September 1960 letter in which the author declares “he had decided to ignore the controversy completely … in order to devote himself to (his) new work.” Addressing his influence on American letters, he claims that “writers such as John Updike and Kurt Vonnegut … had been profoundly influenced by Salinger at a young age,” neglecting that Vonnegut, at least, was a contemporary whose career overlapped Salinger’s almost completely, making the question of influence complicated, if not moot.

More effective are his discussions of the uncollected and unpublished stories, mostly written in the 1940s for magazines such as Story, Cosmopolitan and the Saturday Evening Post. Because these are primarily apprentice works, the material enlarges our understanding of his career. Slawenski, however, overstates Salinger’s influence more than once, assigning his subject a cachet he neither desired nor fully had.

That’s the issue with reading a fan’s notes: the need to elevate the object of one’s desire. At such moments, we lose sight of the real man, the distant husband and father, the loner aware of the gap between himself and others yet unable to bridge it anyway. To be fair, Slawenski touches on this. Still, he never truly gets inside the desolation that seemed to animate the author at his core. The book is particularly thin on the years after Salinger ceased to publish, although to be fair again, how much is there to say? For that, I suppose, we’ll have to wait for the opening of Salinger’s own archive — or to content ourselves with the enigma of not knowing, as the author appears to have intended all along.