Usagi Yojimbo introduced me to a hero trope that I highly enjoy to this day, that of the wandering warrior. It's a well used trope, obviously, and one that's easy for people to connect with, if the popularity of games like Fallout and movies like Yojimbo/Sanjuro, The Man With No Name trilogy, and The Mad Max series are any indication.
My mother's old field guides are another. They didn't kindle my love for nature, but they've been a wonderful supplement while growing up.
There's all those children's books, from folk tales from around the world to Dr. Seuss. From the words to the pictures, they really introduced me to the magic of good story telling.
I can't forget comics in general, as they've been a staple on and off ever since I first learned to read.
Gotta say, I don't think there's a single book that's changed my life, but books as a whole sure as heck have always been a part of it. I definitely wouldn't be who I am today without them.