Adolf Hitler’s reading habits were singular indeed. In the first volume of “Mein Kampf,” written in 1924, Hitler explicitly stated that “reading is no end in itself, but a means to an end.” He explained what this meant:

A man who possesses the art of correct reading will, in studying any book, magazine, or pamphlet, instinctively and immediately perceive everything which in his opinion is worth permanently remembering, either because it is suited to his purpose or generally worth knowing. Once the knowledge he has achieved in this fashion is correctly coordinated within the somehow existing picture of this or that subject created by the imagination, it will function either as a corrective or a complement, thus enhancing either the correctness or the clarity of the picture.

Yet this man with such an anti-intellectual approach to reading came to own an enormous private library of around 16,000 books, kept in his residences in Berlin and Munich, and in the mountain retreat he had built above Berchtesgaden.

The first description of this book collection, published in 1942, divides the volumes into military history, the largest grouping; a section on art and architecture; another comprising many works on astrology, spiritualism, nutrition, and diet, and around a thousand books of often trashy popular literature, including a complete set of the Karl May cowboys-and-Indians stories, of which he was particularly fond. Most of Hitler’s books, those kept in the Reich Chancellery in Berlin, were shipped off by the victorious Soviet authorities to Moscow. They allegedly surfaced in a disused church in the city in the early 1990s, but then disappeared without trace. Many of the books in Munich and at the Berghof near Berchtesgaden fell victim to souvenir hunters among the American soldiers trampling through the ruins of the Reich in Bavaria, but around 3,000, discovered in a Berchtesgaden salt mine, found their way to the Library of Congress in Washington. These were eventually weeded out to leave around 1,200 books — less than 10% of the original collection — that contained undoubted evidence of Hitler’s personal possession. Another 80 books that belonged to Hitler were identified only recently in the basement vault library of Brown University. Others doubtless still exist in private hands.

Hitler did not read, or even look at, most of the books that came into his possession. Many were gifts from admirers or other presentation copies, often finely bound. As an early postwar report on the collection astutely recognized, it was “the typical library of a dilettante,” not of an intellectual or a systematic, educated reader. Nevertheless, that Hitler did read voraciously, if selectively, was remarked upon by those in his inner circle, and by contemporaries. An indication of what interested him most is provided by the marginalia contained in several dozen of the surviving Hitler books.

The “Hitler Library” has in recent years been the subject of a number of studies. What distinguishes the slim, elegantly written, meticulously researched, fascinating volume by Timothy Ryback, “Hitler’s Private Library” (Knopf, 304 pages, $25.95), is his careful analysis of a small, selected number of works that he associates with formative episodes in Hitler’s life. By evaluating the passages that Hitler has underlined, or added marginalia to, Mr. Ryback seeks to extract and elucidate what about the books was important to the man, and moreover what “occupied Hitler in his more private hours, often at pivotal moments in his career.”

Mr. Ryback proceeds chronologically, beginning with one of the earliest works in the collection, a guidebook to Berlin that Hitler bought in France during World War I. It was never plausible, as he reportedly later claimed, that Hitler pored over the works of the lugubrious German philosopher Schopenhauer during World War I. That he carried around with him a guide to Berlin, bought in 1915, and was interested in the artistic and architectural descriptions of the Reich capital, however, matches quite closely what we know of Hitler’s interests. Mr. Ryback ends his chapter on a bizarre note, remarking that he discovered an inch-long black mustache hair in the pages of the book.

From there, his analysis moves to consideration of the influence on Hitler in the early 1920s by one of his mentors, the extreme racist writer Dietrich Eckart, prompted by the latter’s gift of an inscribed copy of his adaptation of “Peer Gynt” — an analysis that perhaps overrates Eckart’s part in the construction of Hitler’s violent anti-Semitism. Discussion of Hitler’s own works, “Mein Kampf” and his “Second Book” of 1928, does not add greatly to what we already know. The absence of serious works of German philosophy in Mr. Ryback’s account of Hitler’s reading habits, and the clear evidence of close reading of tracts on racial typologies and other works on biological racism, many presented by the Munich publisher J.F. Lehmann, also fit our understanding of Hitler’s intellectual world.

Perhaps the most intriguing chapter deals with a number of surviving books in Hitler’s library on spiritual and occult matters. Hitler appears to have shown notable interest in the “demonic” forces and “predetermined fate” in the “man of genius.” As Mr. Ryback aptly adjudges, what Hitler’s attention to such works shows is

Not a profound, unfathomable distillation of the philosophies of Schopenhauer or Nietzsche, but instead a dime-story theory cobbled together from cheap, tendentious paperbacks and esoteric hardcovers, which gave rise to a thin, calculating, bully mendacity rather than some profoundly grounded source of evil, less the triumph of the will than of the shrill.

The last chapters survey a short biography of the military strategist Schlieffen, given to Hitler by his majordomo in the Reich Chancellery, Arthur Kannenberg, in 1940; detail the dictator’s admiration for the book presented to him by the elderly Swedish — and extreme pro-German — explorer Sven Hedin, blaming President Roosevelt for the war, and, finally, examine Thomas Carlyle’s biography of Frederick the Great, which seemed to promise Hitler a last miracle as Roosevelt’s death in April 1945 reminded him (and Goebbels) of the death of the Tsarina Elizabeth, and the sudden change of fortune that followed in the Seven Years’ War of the 18th century.

Thought-provoking as Mr. Ryback’s journey through some of Hitler’s reading matter is, just how many of these books “shaped his life,” as the subtitle has it, remains unclear. For one whose professed mode of reading was to confirm his pre-existing views, the claim that any book was for him a decisive influence is difficult to uphold. Was his life really shaped, for instance, by a guidebook to Berlin that he bought in 1915? Perhaps the subtitle was a publisher’s embellishment, for Mr. Ryback, to be sure, never makes such an explicit claim in the book itself, which in parts provides more background flavor than actual textual analysis. This caveat notwithstanding, Mr. Ryback has produced a valuable short addition to attempts to understand this strange man whose impact on the world was so baleful and of such unparalleled destruction.

Sir Ian Kershaw is a professor at the University of Sheffield and the author of “Hitler, 1899-1936: Hubris,” “Hitler, 1936-1945: Nemesis,” and “Hitler, the Germans, and the Final Solution,” among other works.