The life-cycle of the parasite is also illustrated in a great oatmeal comic :

http://theoatmeal.com/comics/captain_higgins

Peeps, IIRC, was trematodes[1]. After the opening action sequence, the narrator rambles about how trematodes infect snails to get to the birds that eat the snails. Still involves the intermediate host[2] concept, though.

[1] http://en.wikipedia.org/wiki/Trematoda

[2] http://en.wikipedia.org/wiki/Intermediate_host

You can find some more info here (not about the book): http://www.damninteresting.com/a-fluke-of-nature/

I first heard this incredible story about the lancet fluke from Daniel Dennett.

http://www.ted.com/talks/dan_dennett_on_dangerous_memes?lang...

http://www.salon.com/2006/02/08/dennett/

Snail parasites:

https://www.youtube.com/watch?v=EWB_COSUXMw