Zel by Donna Jo Napoli has to be featured in Rapunzel Week or I will feel like I left the week incomplete. Zel is not light reading although it is fine for YA readers. It is my second favorite of Napoli's fairy tale explorations, coming in a close second to The Magic Circle (a book almost impossible to surpass).
Zel explores Rapunzel's psychology, the psychology of all three characters in the tale, including Mother Gothel and the Prince. I haven't reread it in years, but images and feelings remain etched in my memory from my first reading when the book was released years ago and I refresh them every so often, realizing they are still accurate and strong. It is highly recommended especially if you love the tale.
Here's the publisher's description, since I usually include that:
High in the mountains, Zel lives with her mother, who insists they have all they need -- for they have each other. Zel's life is peaceful and protected -- until a chance encounter changes everything. When she meets a beautiful young prince at the market one day, she is profoundly moved by new emotions. But Zel's mother sees the future unfolding -- and she will do the unspeakable to prevent Zel from leaving her...If you haven't read it, do. Don't be afraid of it. It's a beautiful book even with the dark parts--and it is not nearly as severe as Magic Circle. Zel has an unbreakable spirit that is pushed to its limits by confinement, but she triumphs over her adversities. Her loss is stronger for she isn't confined until adolescence when the witch realizes she wants to protect her adopted daughter from her oncoming sexuality and adulthood.