It’s actually happened several times for me.
In junior high, it was the Lord of the Rings trilogy. It fascinated me to such a degree that I studied Tolkien’s invented languages and writing systems, giving over thoughts of becoming an engineer in favor of being a philologist. I outgrew both LOTR and (somewhat later) philology, but my life took a much different track from that point forward.
As a sophomore in high school, it was Hermann Hesse’s Demian; between the Jungian interpretations of LOTR I’d read and this book, it was almost inevitable that I’d spin off down the path of trying to reconcile Christianity with the whole host of other religious and mythological systems that came to my attention, melding them all into something that was supposed to be greater than the sum of its parts. Never was, of course, but once again a book acted on me as an outside force to change the direction and velocity of my life. This is another book (actually, Hesse is an author in general) one has to read as an adolescent or shortly after, or not at all.
I can’t exactly explain why Mikhail Bulgakov’s The Master and Margarita, a satire on the place of the artist in the totalitarian society of the Soviet Union in the 1920s, should have been such an apt book to have fall into my hands during my senior year of high school. Our family had just moved from Fayetteville, Arkansas (as cosmopolitan and liberal as it gets in Arkansas, what with the University and all) to a small town of about 2,000 in the Delta area of Arkansas. This was the poster town for narrow-mindedness, bigotry, anti-intellectualism, and general petty meanness. By some miracle, the local library had a copy of Bulgakov’s masterwork, in the Michael Glenny translation. My efforts to get at everything that’s going on at once in the book started a chain of events that led me to literary studies as my major in college. I continue to re-read it at least once every eighteen months or so.
The next book that profoundly altered my course of life was Thomas Pynchon’s The Crying of Lot 49, during my second year of graduate school. I did a paper on information theory in Lot 49 that I still consider one of the better bits of academic writing I ever did, though a lot of what seemed exciting and arcane in 1987 would now seem trite and mundane in a world grown accustomed to thinking of information as something that can be quantified, encoded, and transmitted with a controllable degree of fidelity. That interest in information theory led me, a few years later, to Jeremy Campbell’s Grammatical Man: Information, Entropy, Language and Life, which first connected for me the information theory concepts I’d become acquainted with through Lot 49 and (then) current ideas about evolutionary biology, the nature of language, and a host of other topics. As a result, I’ve become fascinated with evolutionary biology, evolutionary psychology, genetics, etc. I doubt I’d have read Daniel Dennett, William Calvin, Jared Diamond, Steven Pinker, Robert Wright, Jonathan Weiner, Matt Ridley, RIchard Dawkins, Steve Jones, Antonio Damasio, V.S. Ramachandran, or a number of other scientists and writers without having read Campbell’s book, and I’d not have read it without Lot 49. What I’ve learned from all these sources has dramatically altered my ideas about of human behavior, consciousness, the nature of language, and how the world in general works.