How does your list crossover with mine?
3x or more:
Dragonriders of Pern series by Anne McCaffery
Apprentice Adept series by Piers Anthony
Merlin series by Mary Stewart
Chronicles of Narnia by CS Lewis
Sherlock Holmes (all of them!) by Arthur Conan Doyle
Dream Park by Larry Niven and Stephen Barnes
And those are just the ones at the front of my bookshelf. If I dig I can triple that list. The list of doubles is much longer, and there're many more patiently waiting for me.
What about you?