#3 - Wild Cards by George R. R. Martin et al
Inspired by a Superworld RPG campaign, the stories are generally grim and gritty, and reflect a certain degree of realism in dealing with superpowered aces and hideous jokers afflicted by the DNA-altering "Wild Card" virus. In certain ways, the stories are quite adult, involving a degree of sex and violence that was something of an eye-opener (especially for a series of superhero novels) when I first read them towards the end of the 1980s.
I can't seem to remember right now how I came to buy the UK version of Wild Cards, the first book in the series, with its wonderful cover by Brian Bolland. This book is perhaps not the strongest as it covers about 40 years of altered American history, jumping from one event, and one set of characters to another slightly haphazardly. Still, it sets up a fantastic background and a number of interesting, varied characters for the next umpteen books.
The series has undergone a few changes and is still being produced; the next book Fort Freak is due out later this year. Many of the books between the first 6 and the last 3 are very difficult to get hold of and I don't actually have many of them. Tracking these down at a decent price is something I still occasionally pursue.