To be honest, Cormen et Al. is an actual introductory book. While it is humongous, it covers all of the basic math, logic and algorithms you see in the first 2 or 3 years of an computer science undergraduate course. It is an introduction in the sense that knowing and mastering the tools that the book provides you will set you up for more advanced topics in the many areas of computer science. For instance, a big number of important algorithms in machine learning, computational geometry and other topics use the basic strategies of greedy, divide-and-conquer or dynamic programming algorithms.