Discrete Mathematical Structures

This book sucks. I don't know why colleges and universities use crappy books more often than not. Despite its title, the book doesn't actually bother explaining what the heck is discrete mathematical structures - how it came about, why it is important, what is it used for... It just dives into topics in a confusing manner. The questions asked are sometimes unrelated to the subject material and the answers given at the back at sometimes wrong. What's the point of reading a book and then having to research other books to find out what this book is trying to say and double-checking its answers?