Spook is a book by popular science writer Mary Roach. She is particularly well-known for her book Stiff, a scientific and historical look at what happens to your body after death. This was quite a successful book, and perhaps more importantly, extremely well researched. I suspect the surfeit of research was a primary cause of Spook. It takes over where Stiff left off, being a look a the science and history of afterlife researchers.
The author tells us of anatomists dissecting corpses to try to locate the soul, researchers studying reincarnation in India, attempts to weigh the soul, mediums, people researching the mediums, and, of course, ghosts. It is a wide-ranging exploration, and more entertaining than you may be thinking. Roach brings her excitement and interest -- and her ability to make random connections -- into all matters, no matter how silly or spurious. And she is not shy in mocking those things which are clearly deserving of a good mocking.
Of course, being Roach, she also has a slightly immature sense of what is worthy of our interest; she herself rates her sense of humor at the 4th grade level, although I'd be more likely to put it somewhere around the 7th grade. The result is that we also hear in more detail than we otherwise might about Rabbinical judgments on who is liable in the case of damage caused by a bull penis, Leeuwenhoek's extraction and observation of sperm, a briefly famous occultist who hid pieces of baby rabbits in her vagina so that she could mystically 'give birth', and Gigot de La Peyronie's experiments in extracting and injecting pus from the brain of a teenage boy. All of which is at least tangentially relevant to the issues at hand.
I do not mean to suggest that this book is solely an attempt to entertain at the cost of the spiritually inclined. There is a good bit of science; discussions about the effects of electromagnetic radiation and ultra-low-frequency sound on humans, whether one might misinterpret errant radio broadcasts as ghosts, and so forth. While the bits on the cutting edge of science aren't as technical as I might like, they are well-worth reading, and quite enlightening.
Nor does this book attempt to discredit all belief in the afterlife. Although Roach leans towards skepticism, she does not come to any firm conclusions about the world beyond (although she does have things to say about some of the purveyors of modern mythology). I suppose that she is trying to be fair and balanced in her research, which is fair.
This is one of those book that I don't feel I need to give an opinion on; either you think this sounds interesting, or you don't. I will say that if you are on the borderline, I do find Roach's writing style interesting and fun, and I suspect that you will to. If this book does not sound interesting, I still recommend considering some of her other books, which are a bit more firmly rooted in the hard sciences.