
Graph theory with applications (JA Bondy and USR Murty, available online)
It was one of the only times I had a really bad professor in grad school. He was visiting for six months, and you could really tell he didn't want to be teaching. He used an out of print book (Graph Theory With Applications by Bondy and Murty), which meant I had to go to the library to even read it. He lectured at a level that was beyond us, and he literally wouldn't tell us where his office was, so he wouldn't have to answer questions. Maybe with a different teacher I would have been less annoyed about the research problem.