It all depends on what you like. So I will recommend a few different books.
Slaughterhouse-Five by Kurt Vonnegut (anti-war mixed with humor and sci fi)
The Great Gatsby by F. Scott Fitzgerald. (Generally school required reading)
Inheritance Cycle Series by Christopher Paolini (Eragon, Eldest, Brisinger.) ( Fantasy)
One Flew Over the Cuckoos Nest by Ken Kesey.
A Clockwork Orange by Anthony Burgess (This book is quite obscure and might not be for everyone)
Invisible Monsters by Chuck Palahniuk (this one is quite obscure too)
Harry Potter Series
To Kill a Mockingbird by Harper Lee (generally school required reading)
Of Mice and Men by John Steinbeck (generally school required reading)
Romantic/Character based-The Last Song by Nicholas Sparks
Romance-The Rescue by Nicholas Sparks
Classic-Alice in Wonderland by Lewis Carrol
American-The Adventures of Huckleberry Finn by Mark Twain (however irreverent and possibly insulting it may be for some people)
Slavery-Uncle Tom's Cabin by Harriet Beecher Stowe
Funny-Confessions of a Shopaholic by Sophie Kinsella(and the following books in that series)
Historic-Anne of Green Gables by Lucy Maud Montgomery (and the following books in that series)
Teen-The Princess Diaries by Meg Cabot(Should I even mention the rest of the series?) Also the Clique series by Lisi Harrison for younger teens and Tweens
Short and wild-Night by Elie Wiesel (beware, this is the true story about the holocaust
I must ask, MGGLover, why Of Mice and Men? WHY? Horrible depressing book
Well misse1000, I personally love Of Mice and Men, it just so happens to be one of my top ten favorite books, and yes it may be a sad book but I wouldn't call it horrible. It's an amazing piece of literature and I thought maybe she might like it too