These books will kick your teeth in if you're not prepared. You either get a teacher who'll hold your hand or you need to gear up for fight(develop math maturity and learn all the tricks and tips). To the latter end, you can check out the Book of Proof by Richard Hammack[0] and Discrete Math by Susanna Epp[1].

[0] http://www.people.vcu.edu/~rhammack/BookOfProof/

[1] https://www.amazon.com/Discrete-Mathematics-Applications-Sus...