Humble Book Bundle: Unix
My biggest gripe with this bundle is that they are all digital. I'd rather have less books but then in a printed format. I have noticed that I can't concentrate on reading books when they are presented to me on my computer screen. I do have a kindle (1st or 2nd generation) and that device doesn't support PDF well, furthermore it is rather slow. It works fine for regular books though, where I don't have to flip through chapters back and forth often.