Because I'm a nerd. I like science, and I found the subject matter and the author's writing fascinating. It's always great when you find a science-related book on a subject that interests you and written in a "language" that doesn't constantly fly over your head.
Not an "absolute favorite" but a good and relatively deep book.
This is one of those books that you read a bit from while you're shitting, or just bored at a given moment...I guess you can read through it, but it's not that kind of book for me. Anyway it's pretty fun, and yeah it's about different ways of dying, but it has good humor and tons of interesting tidbits and a fun representation of various different ways in which you could croak.