I read this because the book group I joined but only ever went to once assigned it for September. (And did I go? To sit in a hot tub and discuss it? No.)
So there's this psychiatrist who has a patient who, while under hypnosis, appears to spontaneously regress into past lives. "Catherine" gives detailed accounts of twelve lives lived in different places, as either sex, inhabiting a few different races, as well as information about each death and afterlife experience. The shrink, previously a man of hard science, falls for her sincere and apparently credible tales, especially as each past life corresponds with a phobia she has come to him to help her overcome. As she remembers a life where she was murdered by having her throat slit, she thus overcomes her irrational fear in this life of having her throat slit.
She has other information, too. People in comas can choose to come back or not, depending on if they've finished their "lessons" for this life. She can recognize certain individuals from past lives that she is close to in this one, their relationships playing out similar themes from life to life. The "Masters" look after her after death and help heal the wounds people suffer in life before sending them back into the fray.
A highly emotional book, I let myself get swept up in the romance of it all, the comforting feeling that once we learn all the lessons we're supposed to learn in each life we are looked out for and guided with great wisdom after death. But the other half of my brain went, "Hmm, well, but does her story check out?" The doctor claims that everything she said can be independently verified, that it would be impossible for someone with no experience of rural life to spontaneously describe, while under hypnosis, how to churn butter. (Unless perhaps our brains are capable of storing survival tactics from all those Laura Ingalls Wilder books we read in elementary school.)