Since I haven't seen many discrete maths books, he's my list: Beginner: NL Biggs, Discrete Mathematics, Oxford University Press Intermediate: PJ Cameron, Com

Since I haven't seen many discrete maths books, he's my list: Beginner: NL Biggs, Discrete Mathematics, Oxford University Press Intermediate: PJ Cameron, Combinatorics: Topics, Techniques, Algorithms, Cambridge University Press Advanced: JH van Lint & RM Wilson, A Course in Combinatorics, Cambridge University Press