Good Omens
This is one of my favourite books of all time.
It's a brilliant play on the story of the horror film The Omen, which was about the coming of the anti-christ.
In Good Omens, though, the anti-christ ends up with the wrong family and the well meaning attempts of an angel and a demon to prevent his rise have absolutely no effect. A swirl of sub-plots contain a host of brilliant characters such as Anathema Device - the professional descendent of the only seer to have prophecies that were 100% correct, or Shadwell - the bitterly eccentric leader of the Witchfinder Army (current corps - 2 members), and his well meaning but drippy recruit Newton Pulsifer.
This book is funny, insightful, full of great characters and is a totally great read.
It's on my 'give this book to everyone I know and force them to read it list' - it's that good.
In an interesting sidenote it would appear that I own quite an unusual edition of the book. Nice to know!
The Sandman Companion
This companion to Neil Gaiman's lengthy and wonderful Sandman comic epic derives most of it's merit from a in depth interview with the man himself.