Very high on my list. I've read it several times.
Books are like guns. If you know how many you have, you don't have enough. I don't know if I have a copy of "This Perfect Day" or not.
Another book I recall enjoying was "Dark December", at least in part because it took place near where I was living. I don't remember much about it now.
Phillip Jose Farmer wrote a short novella-Riders of the Purple Wage-in 1967 that I’ve read countless times, too. It is about the welfare state, and is one of the most hilarious stories I have ever read-it even has a happy ending.