I collected the following "top eight" text books on computability (in alphabetical order):
Boolos et al., Computability and Logic
Cooper, Computability Theory
Hopcroft et al., Introduction to Automata Theory, Languages, and Computation
(thanks to Bill Province)Kleene, Introduction to Metamathematics
Minsky, Computation
Sipser, Introduction to the Theory of Computation
(thanks to Prajwal Kansakar)
I know it's opinion-based, but which important text books did I miss?
Hopcraft, Motwani and Ullman, Introduction to Automata Theory, Languages, and Computation