The book Zero Day is an instant computer security classic. Unlike The Cuckoo's egg (which I also recommend), Zero Day is a fictional story, but not at all less plausible.
It's very fun to read, with a captivating plot. I kept flipping to the back cover making sure I remembered correctly, that the author is a computer security expert who wrote sysinternals, a hardcore system administration tool for Windows -- He may well have been a professional novelist.
Its target audience is not limited to computer professionals, but computer geeks should really enjoy it. When it gets technical, the author does a great job at explaining the terms, and the technical parts are extremely accurate. I'm quite familiar with the technology though, so I'm probably biased -- others might find it too technical for their taste.
The threat of attacks against big Western companies isn't imaginary -- RSA and Google among many others have been the targets of attacks just like the ones described in the book. When the purpose of the attack becomes destruction, the story is certainly more interesting.