Good Omens, by Neil Gaiman and Terry Pratchett

What can I say? If you know that it's a mixture of Gaiman & Pratchett, and you know either of their work, it will be exactly what you're expecting. Also, I think the quote about it being a direct descendant of Douglas Adams's Hitchhiker's Guide to the Galaxy is pretty darn accurate as well. (One caveat - the religious (or at least devoutly Christian) will probably not like or get it, and will probably end up rather offended. So if that's you, maybe skip it.)