My favorite books today are Water for Elephants and The Time Traveler's Wife. But I have a favorite old book that I read every couple of years, it's Thurston House by Danielle Steele. Even though I don't usually read her books, Thurston House has been an a favorite of mine for more than 20 years.
Yup, that's one of my "if you were stranded on a desert island" books. Others would be Gone With the Wind, Strangers (Dean Koontz) and probably Raptor & Aztec by Gary Jennings - an incredible author, but NOT for the faint-hearted.