Unfortunately, what we cover is not available in any one book. However, most of the material is touched on, to a better or worse degree, in many textbooks. So, I have listed four textbooks as places you can look when what I said in class was unclear, or for any other reason you want a second opinion. What I strongly do encourage is for you to find a few other students enrolled in 360N and form a study group. I further encourage each member of a study group to buy a different one of the four optional books, and for all members of the study group to share the books.
Some students remain unconvinced and insist on going it alone.
You will do better working together. More talented students will solidify deeper understanding of the concepts as a result of explaining things to less talented students. And less talented students will do much better as a result of the interaction with more talented peers in the class. So, yes, I think you should buy one of the four optional books as a second source to the material I will cover. Which one does not matter.