Being a final year Mathematics degree student, I have seen my fair share of Maths books. Of these, Prof Truss' "Discrete Mathematics for Computer Scientists" is among the best. The definitions are accurate and the structure of the book is highly intuitive. This book has proved to be an extremely useful resource for me over the last two years, covering graph theory, ring theory, logic, computability and more. I would strongly recommend anyone with any interest at all in discrete maths or algebra to obtain a copy of this book.
"Discrete Mathematics for Computer Scientists" covers a number of topics in Mathematics but still goes into considerable detail in each of these. I bought this book hoping it would help me with the mathematical logic module I was studying at the time. Instead, it helped me with my whole degree!