Concrete Mathematics is more pleasurable to read than the first part of TAOCP which covers more or less the same material.
Introduction to the Theory of Computation is good. You can get a used copy of the first edition (on Amazon) for significantly less money than the second edition, and, being that this book is very overpriced in the first place, this might be the best way to go, unless you're really interested in some 2nd-edition improvements.
Despite the title, I've heard of several others, but haven't read them at all. The Patterson books on computer architecture are said to be good, and I've seen them on the shelves of co-workers (though they've seen a can of Spam on my shelf, and I really don't like to eat Spam, so, who's to say what a book sitting on a shelf actually indicates?)
I've heard of the third one, Concrete Mathematics.
I vaguely remember reading of the 4th, HOPL 2, and the 5th, Computer Organisation and Design. As far as I recall, they are good actually.
I might have heard of CTM before, but that's about it from this list.
The HOPL book has a big paper about the history of Lisp and dozens of pages of Chuck Moore, Icon, and Prolog AI chatting in French. What more do you need? (Also: Smalltalk. C.)
CTM is the best thing ever.
Any opinions?