Garp
Since childhood, when my Grandpa read me the works of Robert Service and Jack London, I've been a fan of just plain stories. There's something about a well-written tale that can take you from the life you know and drop you into a completely different world... but do it in a way that you can still identify with the characters... and think of them like people that you know.
Probably my favourite book of all time is Farley Mowat's The Dog Who Wouldn't Be. It's not considered one of the great works of the literary canon and it doesn't raise complex issues about life, death, or religion. It's just a really good story about a boy and his dog. Although much of it is autobiographical, even Mowat admits that most of the story is embellished beyond reality.
A close second, is John Irving's The World According to Garp. Irving's novel is like reading the diary of someone you barely know... and by the second or third chapter, you feel like you have an investment in the main characters. It's a remarkable feeling to be caught up in ficticious events as you would in your own life, but this book has that power. Unlike stories like Lewis' Narina series or Tolkien's novels which dazzle with graphic description, these novels use action to draw the reader to characters.
I'd forgotten how much I loved these books until a recent conversation with Jen about Garp. I really should visit him again sometime soon.