Chaos Mode — Piers Anthony

The third chapter in the Mode saga reunites some old friends...Colene, the young woman from Earth grappling with terrible suicidal depressions... Darius, the king from another planet who won her love... and Seqiro, the telepathic horse who shares their incredible journeys. Together they travel a shimmering path between the parallel universes that are both wondrous and dangerous.

Now Colene and her friends are embarking on their most daunting adventure yet. Going with them is a strange new friend named Burgess--a tentacled alien unlike any known. They're all heading back to Earth, where Colene can make peace with her estranged parents. And put to rest the childhood events that have been haunting her soul for a very long time...