Here are some "books that changed my life" in various ways -- personally, culturally, professionally. There are many more books I can recommend, but these are good books that actually brought about significant change in my life (as opposed to books which are simply good), and as such is rather personal and eclectic.
M. Scott Peck, The Road Less Traveled. "Life is difficult." This book talks about how to deal with this. Peck is a therapist and the book has many illuminating and moving case studies. He talks about love, self-discipline, and spiritual growth. I started this book in mid-90s, and it didn't grab me. In November 1999 a chance conversation with a friend serendipitously led me again to the book, and this time I was in the right mental state for it, and it was a catalyst for major change. E.g., having read this book played a major role in my starting to draw again, discovering yoga, and creating this web site. Based on my experience, you may need to be in a time of upheaval in your life for this book to seem useful. On the other hand, I know lots of people who've read it and loved it at various times in their lives.
Alan Moore & Dave Gibbons, Watchmen. This is the comic book/graphic novel which got me hooked on comics in my mid-20s. (I'd only occasionally been into comics as a kid, never taking them very seriously.) It's a 12 issue story about superheroes for people who aren't into superhero comics. It's full of literary cleverness, good art, fascinating characters, twisted psychology, social & political commentary; plus it has an engrossing story with a central mystery. This is the one that made me realize comics can be good serious literature. Watchmen's comic-within-the-comic, Tales of the Black Freighter, inspired the name of my & Brendan's partnership Black Freighter and led me to a new appreciation of the wonderful music of Kurt Weill as a side effect (the Broadway revival of Threepenny Opera uses the phrase "Black Freighter" in its translation of the song "Pirate Jenny".) Watchmen has caused all sorts of unexpected events in my life!
Doug Atkinson wrote some nifty annotations stored at R.J. White's site. Ralf Hildebrandt also has annotations.
In March 2000 I began drawing a series of Bench comic strips that are an homage to Watchmen.
Here's a cute single-panel homage done by Jonathan Thayer, "When the Kollumaņeros dress up as DC Comics's Watchmen".
Ludovico Ariosto, Orlando Furioso. A huge sprawling epic Italian chivalric romance from the early 1500s! I read this in Douglass Parker's Parageography class at UT and was completely swept away. Magic, adventure, romance, intrigue, stories within stories, a huge cast of characters running all over the place, even a trip to the moon to retrieve mad Orlando's lost wits. That gave me the idea of a (still unwritten) story about General Sherman running amok in Georgia, told in the style of an epic romance, and by this curious chain of weird brainstorms, I became seriously interested in the American Civil War before Ken Burns made it cool... So reading Orlando Furioso was the cause of my multiple road trips visiting various Civil War sites. That's just the sort of delightful unexpected detours that happen in the book... The book has of course influenced much later art and literature, including Shakespeare's Orlando running amok in the forest of Arden (As You Like It); March 3 2000 I saw Handel's opera Alcina at UT, which retells a story from Orlando Furioso.
John Lakos, Large Scale C++ Software Design. This book changed the way I program. He argues persuasively for automated unit testing of each module, and an architecture with no cyclic dependencies between modules. The latter sounds impossible to many people, but he presents techniques to accomplish it in C++. Much of the book reads like obvious common sense, then you stop and think "Wait a minute, if this is so obvious, why don't we program this way?" We began applying his suggestions on a large C++ project and were quite pleased with the results.
Bertrand Meyer, Object Oriented Software Construction. This book changed the way I wanted to program, made me more conscious of my disenchantment with C++, and indirectly led me to quit my job, so read it at your own risk! Like Lakos's book, much of this book had the ring of obvious truth, yet its principles are not widely used. The book is well worth reading regardless of what language you program with, but to fully use Meyer's ideas requires the Eiffel language. The whole Design-By-Contract model is wonderful, making assertions in C/C++ pale in comparison (and the complete lack of assertions in Java is mind-boggling). A subtly different model of generic programming (templates in C++) and multiple inheritance gives much food for thought. The Eiffel language (designed by Meyer about the same time as Stroustrup was designing C++) has not caught on like C++ did, and so the tool support is not nearly as good as C++ tool support, sadly, nor are the libraries or language as standardized. If you want to start online, go to www.eiffel.com or www.elj.com. There is also a newsgroup comp.lang.eiffel.