A nice introduction book to the theory in Computer Science.

The book is free thanks to both those "masters" authors Aho (http://www.cs.columbia.edu/~aho/) and Ullman (http://infolab.stanford.edu/~ullman)

Follows the table of contents

Preface
Table of Contents
Chapter 1 Computer Science: The Mechanization of Abstraction
Chapter 2 Iteration, Induction, and Recursion
Chapter 3 The Running Time of Programs
Chapter 4 Combinatorics and Probability
Chapter 5 The Tree Data Model
Chapter 6 The List Data Model
Chapter 7 The Set Data Model
Chapter 8 The Relational Data Model
Chapter 9 The Graph Data Model
Chapter 10 Patterns, Automata, and Regular Expressions
Chapter 11 Recursive Description of Patterns
Chapter 12 Propositional Logic
Chapter 13 Using Logic to Design Computer Components
Chapter 14 Predicate Logic
Index 

Follows the link down below:

http://infolab.stanford.edu/%7Eullman/focs.html

Comment

The book has a different structure than usual computer theory book, I like it personally.