I took Sipser's class and read his book. I found Barak's textbook pretty good after that. You can read it out of order, and it has pretty good citations so you

I took Sipser's class and read his book. I found Barak's textbook pretty good after that. You can read it out of order, and it has pretty good citations so you can always look confusing topics on your own. "Computation Complexity: A Modern Approach" by Arora and Barak