Gulp is definitely light, popular science, with an abundance of footnotes, irreverent comments, and some interesting facts/experiences. I wasn’t grossed out by it, since I can be fairly clinical, and rolled my eyes at some of the humour aimed at being gross; mostly it was an interesting read, certainly a quick one. It’s accessible, no matter what level your knowledge of biology is at, mostly dealing with the various topics in an anecdotal way.
I liked reading it, but now I have and look back, I think it dragged a little. Part of that’s doubtless my sense of humour, which is defective and needs to be returned for a refund. Part of that is the endlessly anecdotal nature of it. I’ve reserved another of Roach’s books from the library, but I wouldn’t buy it for myself; I do have a friend who I think would find this quite interesting.
Also, will people please quit hurrhurrhurring at the idea of faecal transplants? I’m sure it’s all very well to laugh at it from a distance, but a) it’s reinforcing the stigma about diseases like Crohn’s or ulcerative colitis which really are not funny, and b) I have high hopes that they will actually find a way to cure or at least greatly alleviate inflammatory bowel diseases as a result of studies into this kind of thing. Several close friends have IBDs, and I cannot wait for the day they can quit feeling that shame/disgust.