The Gods of Mars Barsoom Series, Book 2 by Edgar Rice Burroughs

Soldier and adventurer John Carter tells the story of how he returns to the planet Mars to be reunited with his love, the Martian princess Dejah Thoris.
With his great friend Tars Tarkas, mighty Jeddak of Thark, Carter sets out in search of his princess. But Dejah Thoris has vanished. And Carter becomes trapped in the legendary Eden of Mars, from which none has ever escaped alive.