CS Lewis - Narnia, or his space trilogy starting with Out of the Silent Planet.
Mary Stewart - The Crystal Cave, the Hollow Hills, etc
John Wyndham - The Chrysalids and The Day of the Triffids and others.
These are not new and may not appeal to modern teen, but the stories are classics, and their morals are solid.
The family overseers will recognize them, but the books are not preachy.
For something more modern, try Connie Willis' Doomsday Book.