[indogooner]

J Hopcroft, JD Ullman, R Motwani, Introduction to Automata Theory, Languages and Computation

I have heard M Sipser's book is also good but have not gone through it myself.

[skydhash]

Sipser’s is quite good and more introductory than most. You can try also Code by C. Petzold if you need some general understanding about computers and also Lectures on Computation by R. Freynman. And MIT OCW have lectures by Sipser.