I have just read John Brunner's The Shockwave Rider yet again; in fact, I have probably read this more times than any other single book.
It's a cyber-punk novel written ten years before the genre was recognised. It was rather poorly received, both because it was seen as too fantastical (in many respects it wasn't), and because its style is rather disjointed (it works for me); the rather moralistic ending is weakly done, even though it fits the theme of the book just fine. In many respects the book has also dated somewhat, which was inevitable - however, it was also the book that gave us the term "computer worm". The inspiration for the book was Alvin Toffler's Future Shock, hence the title.
The idea in it that resonates so strongly with me that I keep coming back to it is the importance of individuality, and of recognising and nurturing it. The depiction of what happens when this recognition is lost may be extreme, and strained at times; but it never seems to me to go beyond the bounds of possibility, in the sense that I can picture people who would be pleased to build such a future. I would wish to forestall such people before they reached this point.