I'm going to be at an REU for discrete math and combinatorics over the summer. Do you have suggestions for combinatorics books to look at? An introduction to graph theory would especially help (I'm taking an algorithms class but I doubt that it would go into much depth regarding graph theory)? I think the book "A Walk Through Combinatorics" (Bona) is quite good for a general overview of combinatorics, but I'm also wondering about what other things I could look at. Also, any suggestions for a number theory book for someone already familiar with elementary number theory and some background in algebra?