I actually just bought Rosen's 'Discrete Math and Applications' on amazon. My college education was in art, so needless to say, not much mathematical training in my undergrad education. In my current job I'm a web developer and I've been trying to cover a CS knowledge base through self study. Through reading reviews about discrete mathematics books I was pointed towards Epps' 'Discrete Math with Applications' http://amzn.com/0495391328 and Rosen's book. I was told Epps' book doesn't go into as much depth, but doesn't assume any prior knowledge from the student. This is great for someone like me with an art degree and the will to learn discrete math. All this is tangentially related to why I'm posting. All of these books mentioned are really expensive, mostly because they are used in college classes. A trick I've started using is buying previous additions of these books for pennies on the dollar. I got Rosen's fifth edition for $7 as opposed to ~$160 for the seventh. After reading the update pages online, I don't think I really miss all that much doing this either.