I guess I had forgotten how much there is--I was a Heinlein reader sub-teen but in general lost interest in SciFi--this book and "Contact" (and maybe "Broca's Brain") are the only ones that come to mind since then (unless you want to include George Orwell, Aldous Huxley, Ayn Rand, and George Lucas).
I mentioned "P-1" here because it is the only one of the lot (that I can remember) where the _network_ is a (the) major protagonist.