Overall I really enjoyed this book. I'm a person who is interested in the history of medicine and biology and genetics, so I found this book very very interesting. If you are not into that sort of stuff, however, you might not like this book.
There were a few things that bothered me though. For one, the chapters jump around a lot. Let me explain. Each chapter is titled after an organism that contributed to biology (like, guinea pigs and fruit flys), but the individual chapters jump around a lot, and don't always stay on topic. The last chapter, which is titled: OncoMouse, only mentions that critter a few times (which is fine, but if you're going to talk about other stuff, call the chapter something else). Another thing that bothered me was the number of typos. There weren't too many, maybe one or two per chapter, but I found the that overall it was very distracting.
That's not to say that I didn't like this book. On the contrary, I liked it very much. I loved that it really is what it says it is: A guinea pig's (and other creatures) history of biology. It's giving thanks to them many plants and animals that have contributed to our understanding of biology. I liked this because I feel that while people are usually given thanks for their contributions, the plants and animals seldom are. Another thing I liked was the stories. The books didn't just talk about the animals, but gave stories to illustrate specific examples of how the critter in question contributed. And it also gave a history of the plant or animal itself. For example, the chapter on guinea pigs talks about where the animal came form and how it ended up as a household pet and lab animal.
Overall I think this book is fantastic, and an absolute must read for anyone at all interested in the subject!