The Chronicles of Narnia
by Todd Matthy
The Chronicles of Narnia were written by Tolkien's contemporary and good friend C.S. Lewis.
It is an epic series of novels about a group of four young siblings who enter a magical realm through various portals, and team up with Aslan, a Christ-like lion, to save the land of Narnia from it's enemies.
Simple and allegorical these books are deceptively one of the richest fantasy series of all time despite their short length.
Definitely the follow up (or in some cases precursor) for readers of Tolkien.
The kind of books that stay in your heart forever.