My favorite book is actually a trilogy & I think I can get away with naming 3 books as my favorite "book" because each book is a continuation of the one before it. The Dragonlance Chronicles consists of 3 books - Dragons of Autumn Twilight, Dragons of Winter Night, & Dragons of Spring Dawning. I first read the DL Chronicles when I was living in New York - a boy that lived in our apartment complex had let me borrow them. It was right around the time my parents were having marital problems & this was when I was just starting to read fantasy books. I was around 11 years old.
Reading these books has forever shaped the person that I became today & it instilled within me the love of anything fantasy. I was too young to read into the story and simply took it at face value - the story of a courageous band of friends who were looking for something to believe in & who had to overcome many adversities to find what they needed. Sure, there are many stereotypes involved in this story, heavy borrowing from Tolkien and whatnot but I can still read these books today and be completely drawn into them, the same way I was when I was 11 years old.