I'm not going to offer a '100 best books' list but I'll mention a few American novels I've particularly enjoyed.
Mark Twain - Huckleberry Finn
Herman Melville - Moby Dick
Nathaniel Hawthorne - The Scarlet Letter
Henry James - The Golden Bowl
Ernest Hemingway - A Farewell to Arms
John Steinbeck - Of Mice and Men
Richard Powell - Don Quixote USA (one of the funniest novels I've ever read)
Alfred Grossman - Marie Beginning (almost as funny as Powell and his satire has a lot more bite)
Maxine Kumin - A Daughter and Her Loves
F M Busby - Rissa Kerguelen (one of the greatest science fiction novels ever written)
Suzy McKee Charnas - Walk to the End of the World (a great science fiction dystopia)
Lynn Abbey - Daughter of the Bright Moon (a great fantasy novel with a strong female protagonist)
Maya Angelou - I Know Why the Caged Bird Sings (beautifully written and heartbreaking)
That should do for starters!