Two categories: Theory - About Some technology (Score 1)

I would order them by Theoretical ones, because this books tend to long more years. For example: The books of Knuth and the books of Cormen. The books that talk about some technology, "expire" faster, most of people don't want to read a book about some programming language/Operative System of the 90's or before. After this big categories, you can follow the sugerence of other slashdotters.