The Steel of Raithskar

From Wikipedia: Ricardo Carillo, an aging language professor with a terminal illness, is flirting with a captivating young woman on a Mediterranean cruise ship. They both watch with wonder, and a growing horror, as a dazzlingly beautiful star quickly grows to engulf the sky and then crashes into the ship. Ricardo awakens in a blinding hot desert, with no idea where he is and a dead man by his side. Without knowing how or why, Ricardo finds himself inhabiting the body of a strong, healthy, young man named Markasset. Ricardo quickly learns that Markasset is wanted for murder and the theft of a precious and powerful gemstone, the Ra'ira. Ricardo has only a smattering of Markasset's memories, and no idea if he is guilty or innocent. But with the help of a giant warcat named Keeshah, with whom he shares a telepathic bond, and the beautiful illusionist, Tarani, Ricardo sets out on a quest to recover the missing gemstone and clear his new name. But what has happened to Markasset? And when will he want his body back? Now that he has a new lease on life, can Ricardo let it go? The series is full of vivid characters, sword play, great warcats, and a desert world called Gandalara...a kind of alien Arabian Nights. Originally released as seven novels, the series was repackaged into three volumes (The Gandalara Cycle I, The Gandalara Cycle II, & The River Wall). In the 1986 edition of the Gandalara Cycle II two of the books are out of order. The Search for KÄ appears after Return to Eddarta