The Master Mind of Mars by Edgar Rice Burroughs [Barsoom #6]

THE MASTER MIND OF MARS is the sixth in Edgar Rice Burroughs' BARSOOM series. The story follows Ulysses Paxton, an Englishman transported to the red planet by astral projection. Paxton is taken in by Ras Thavas (the 'Master Mind'), an aging mad scientist who has perfected the art of transplanting brains from the aging bodies of the rich to younger, healthy bodies. This comes at a terrible price, the death of the young victims of the Master Mind.