So many great books, so little time to read them all. I just finished rereading Jack London's "Call of the Wild." It's a great boy's book and adults will find it terrific as well. I thoroughly enjoy reading the early S. E. Hinton teen novels--"The Outsiders," "That Was Then, This Is Now," "Rumble Fish," etc. And for a futuristic look at a controlled world, you might give "The Giver" a try.
My absolute favorite leisure book is Lamb, by Christopher Moore. It's the gospel according to "Biff", Christ's childhood pal. Many people are turned off by the title, as they feel it is sacrilegious in some way. However, it is used as a text in seminary schools, and many congregations read it together as a community. It combines humor & critical thinking about the Bible and Christianity, but mostly it explores Jesus in his incarnation as a man. His relationship to Biff (who's the ultimate archetype of a trickster) is incredibly moving. It's really quite fascinating, & easily one of the funniest books I've ever read. I think that, if actually read, it would appeal to anyone, no matter what culture, religion, or creed.
I agree on the choice of Speak, as I think it is very powerful. Carl Hiassen's Hoot is another good read in terms of combining adolescent concerns with social issues, in particular environmental awareness. It is also a quick read and one that can be read for leisure.
I really liked Fup by Jim Dodge.