The main protagonist of "The Jacket" is Darrell Standing, a university professor serving life imprisonment in San Quentin State Prison for murder.
Due to some low-level intrigue amongst prisoners, he is suspected of hiding dynamite and sent to solitary confinement. There he is put into the jacket, a canvas jacket which is tightly laced to compress the whole body and at first he experiences excruciating pain. However, another prisoner, Ed Morrell introduces him to a "trick" that would make his condition in the jacket tolerable.
He is introduced to a technique of entering a trance-like state where your conscience is freed from the constraints of your body and is free to roam the universe. Once Standing accomplishes this state of mind, he starts to recall episodes from what he believes are his previous lives. These various episodes form the bulk of the narrative in the book. The parts about the prison are brutal and horrifying and the sequences of past life recall detracts from this in part but it's still a very good read.
When Jack London wrote this the jacket was actually being used in San Quentin and London's descriptions of it are based on interviews he had with an ex prisoner called Ed Morrell who had spent five years in solitary.
Although written almost 100 years ago, it's still a powerful read, it's a shame its had under 250 downloads on Gutenberg and is available for free here