These are books that are re-tellings or variations on classics and Shakespeare.  The books are grouped according to what book or play they are related.

Hamlet

Hamlet by James Marsden

Something Rotten: A Horatio Wilkes mystery by Alan Gratz

Dating Hamlet: Ophelia's Story by Lisa Fiedler

Ophelia's Fan by Christine Balint

Undiscovered Country by Lin Enger

King Lear

A Thousand Acres by Jane Smiley

Macbeth

Lady Macbeth by Susan Fraser King

Enter Three Witches by Caroline Cooney

Lady Macbeth's Daughter by Lisa Klein

Much Ado about Nothing

Confessions of a Triple Shot Betty by Jody Gehman

Mythology

Nightsong and Starfall by Michael Cadnum

Oh My Gods by Tera Lynn Childs

Goddess of Yesterday by Caroline Cooney

Corydon & the Island of Mountains (first in the series) by Tobias Druitt

Nobody's Princess and Tempting Fate by Esther Friesner

Lavinia by Ursula LeGuin

Cupid: A Tale of Love and Desire by Julius Lester

The Night Tourist (Orpheus) by Katherine Marsh

The Great God Pan by Donna Jo Napoli

The Lightning Thief (first in series - modern day meets mythology) by Rick Riordan

The Haunting of Drang Island (Norse mythology) by Arthur G. Slade

Quicksilver and Quiver by Stephanie Spinner

Othello

Exposure by Mal Peet

Pygmalion

The Fat Girl by Marily Sachs

Romeo and Juliette

Romeo's Ex by Lisa Fielder

Romiette and Julio by Sharon Draper

Shakespeare in General

Loving Will Shakespeare by Carolyn Meyer

The Tempest

Ariel by Tiffany Grace