Piers Anthony

There is trouble in Xanth again because the Gap Dragon escaped and is ravaging across the land.

A quest for the source of power threatened to doom the land of Xanth
As a ruler of a country steeped in enchantment, King Trent was naturally curious about the source of its magic. It made sense to order Bink, the only one of his subjects immune to supernatural harm, to undertake a quest to discover the wellspring of Xanth’s uniqueness.
From the beginning, Bink and his companions, Chester the centaur and Crombie, the soldier transformed...

In the first book of the Adept trilogy, someone is trying to destroy Proton, and Stile's survival depends on mastering magic and winning the Great Games.

When a Nymph rides a Night Mare, Ogre beware!
Smash knew all about ogres. After all, despite his having a human mother, Smash was an ogre himself. Ogres were not only huge and horribly ugly, as Smash was; they were also so stupid they could hardly speak, and they spent most of their time fighting, destroying, and eating young girls.
So what was he doing here with seven assorted females looking to him to guide them and save them? Even...

A knight of ghosts and shadows!
Jordan was a ghost in Castle Roogna now, spending his time with little five-year-old Ivy and watching his own past unfold on the magic tapestry. But once he had been a valorous knight, riding his ghost horse Pook on a fabulous and dangerous mission.
He had been betrayed with a cruel lie by two wily magicians and the woman he loved. He had been killed at the end, and his bones had been scattered. Now he...

"Squid may only be a tween alien cuttlefish, but her feelings for Chaos, her Demon boyfriend, are real, which is why she's more than ready to let someone else take over as the protagonist of this story. Being a main character is exhausting--and it's drastically cutting down her flirting time with Chaos. But their alternate future is dependent upon their completion of one final mission... Seven years from now, in another reality frame, things are not...

Upgrading her shape-changing abilities to lead a mission against an adversarial Demon, Squid joins a covert group disguised as traveling dancers before new friendships and a growing bond with a secret companion challenge their goals.

Searching for a missing sorcerer is a perfect chance for Prince Dolph, a Xanth shape-shifter, to see the world. Setting off with his faithful companion Marrow, he will penetrate the island of illusion, escape a goblin kingdom, outwit a mermaid, nest-sit for fiery dragons, and find romance with a princess.