The mostly undeclared focus of the book is how all of these encounters have influenced his writing; he spends almost as much time talking about how it feels to know you can be eaten/killed/completely ignored by something as he does talking about the animals themselves. He doesn't explicitly talk about what events inspired what novels until the last chapter but you can see hints and references throughout if you're familiar with his books.

You can also see the roots of some of the ecological/environmental elements I've seen in his fiction - especially having respect for the wilderness/flora/fauna around you.

I think you'll get more out of this book if you've read some of his work but even if you haven't, it's an interesting look at how any fantasy/sci-fi writer might get ideas for some of their monsters. (Though how you're supposed to go on safaris and such if you're not already a popular author with lots of cash, I've no idea.)