Best-selling British fantasy author Simon R. Green's latest offering is Just Another Judgement Day, which takes place in his popular Nightside milieu, a fictional city where you can find anything ... if it doesn't find you first.

"[There, you'll find] forbidden knowledge and forgotten secrets, every sin you can think of and all the pleasures that may not have a name, but certainly have a price," Green said in an interview. "It's always night in the Nightside, perhaps because the sun is ashamed to show its face there. Or because someone would steal it. Everyone comes to the Nightside, sooner or later. And gets into the kind of trouble that only John Taylor can get them out of."

Taylor is a private eye with a gift for finding people and things and for getting into more trouble than one man should have to put up with. "[He] wouldn't know a clue if he fell over it, but he will find the truth for his client, whatever it takes," Green said. "Basically, Taylor operates in the twilight zone, investigating cases of the weird and uncanny."

In Just Another Judgement Day, Nightside is visited by the Walking Man—a man given the power by God to avenge the injured and punish the guilty. Given that the Nightside is such a haven for sin and sinners, he's going to have his work cut out for him. And so will John Taylor, keeping the Walking Man from simply killing everyone in his path.

The fictional city of Nightside is based on the part of London called Soho as it was in the '70s. "It was a dark and scarily glamorous place, with the best bars and clubs in the world and people on the way up and on the way down," Green said. "And a celebrity on every street corner, doing something unwise. ... To research this book, I had to go to appalling parts of London and talk and drink and generally cavort with all kinds of appalling people. And then claim it all against taxes."

After this book, there will be three more entries in the Nightside series, and then it will come to an end. But Green currently has another ongoing series called Secret Histories, the next installment of which—The Spy Who Haunted Me—will be out this summer.