Having seen the movie before reading the book, I was surprised to find the various differences as I made my way through the book, in particular; the ending.
It's such a sad, unfair story about animal experimentation and how a pair of dogs try to understand why, and survive in a world they didn't deserve to suffer in.
As for the writing, I felt that the author sometimes got carried away on random tangents. But I found the various written accents to give a lot of character, they were a bit hard to understand sometimes.