Occasionally, somebody will refer to a book and sigh, "that book changed my life." I nod, like I know what they're talking about, but I really tend to be thinking "...really?"
Frequently, I've read the book as well. Life of Pi? Didn't change my life. Neither did The Kite Runner, though it made me profoundly frustrated and angry. The Help? Nope.
Maybe The Fountainhead did, to a small degree, but maybe I don't want to make declarations like that here.
Maybe life-changing ability isn't what I read books for. Maybe, because I also write books, I don't look at them as mystical tomes that hold profound answers. I love to read, anybody who knows me will be able to attest to that (and if they aren't able, I guess they don't know me), but maybe what I want to get out of a book isn't what others seek.
I look for entertainment in books. When I open a book, I certainly do want it to take me away for a little while. Books are education, books are thought exercises, books are fantasy, books are time travel. American Gods, by Neil Gaiman, contained things I'd never thought of before. I'm looking forward to reading the anniversary edition, which I've brought home from the library yet again. Did American Gods change my life? Not more than The Fountainhead, anyway.
So really, I do feel that a book's job is to create an immersive world that I go and visit for a little while. No more, no less, though really, that's a pretty tall order. A book that I continue to think about after I've closed it, that's a good book. The Hobbit and Lord of the Rings both take place in a complete world of Tolkein's creation. They have been, and will continue to be, popular for just that reason. The movies have only added to that, and with The Hobbit releasing trailers, will continue to.
Tabletop fantasy role playing games indeed owe a profound debt to Tolkein (well, and war gamers), because the world he created still has such a profound effect on the fantasy worlds that are created today. Indeed, "traditional fantasy" makes one think of elves, and orcs, and goblins, swords and sorcery. Urban fantasy frequently has these elements as well.
So yeah. The book that changed my life? Well, it's a few I guess, but one of them was referred to as The Player's Handbook, and was 3rd edition Dungeons and Dragons, published by Wizards of the Coast. Before I had friends who had that book, and others, I didn't know. I didn't know that, other than in theatre, people came together to tell a story together, acting out characters who have no scripts but very certainly have specific roles. I didn't know about White Wolf either, publishers of The World of Darkness, old and new.
Gaming can be better than workshopping. Gaming can fuel the fire to write, within those consensual worlds, and in others of your creation. It can make you push your boundaries and test the edges of trust, and make you think hard about the decisions that you're willing to make. As a writer, it's been a blessing to me, and a good game is equivalent to a good book.
D&D, unfortunately, moved to other editions, and 4th edition is where Wizards of the Coast and my gaming group parted ways. We're partial to Pathfinder, now, by Paizo publishing. It maintains that spirit of the game, the traditions of orcs and elves and goblins, and wizards with staves casting spells.