Pandaemonium or Pandemonium (American-English) is the name invented by John Milton for the capitol of Hell, it's name is normally translated as All-Demon-Place. The high capitol was built by fallen angels at the suggestion of Mammon & was designed by the architect Mulciber, who before his fall designed palaces in heaven.
Christopher Brookmyre's Pandaemonium Is the story of the pupils of St Peter's High School & what happens on their retreat at a secluded outdoor activity centre set in the wilds of Scotland. They are on this retreat to try to come terms with the murder of a fellow pupil, this will involve the usual techniques of counselling, contemplation & prayer - not to mention booze, drugs, sexual liaisons & a great deal of partying.
Buried beneath a mountain, the US army has a secret base, in which they have some how opened a mysterious portal, from which hordes of big scary creatures with horns & tails come pouring out. Thinking that they've discovered an entrance to Hell & being the military, they slam a lid on it, and send for the artillery, which in this case is Cardinal Tullian, head of The Congregation for the Doctrine of the Faith, formerly known as The Inquisition. There's a lot of experimenting on the creatures (holy water, Crucifixion etc.) there is also lots of bad feeling as the scientist are being replaced by the churches brethren.
Back at the retreat the pupils are getting ready for a disco, with planned shenanigans aplenty.
Guess what happens ?
Yes, ALL Hell Breaks Loose.
Christopher Brookmyre, says on the back of this book "Two very different worlds are about to clash in an earthly battle between science and the supernatural, philosophy and faith, civilisation and savagery.
The Bookies are offering evens."
The battle that ensues between the two opposing factions becomes a bloodbath where everything found is a weapon from pitchforks & other farming implements to guns & bows. Chainsaws are used to bludgeon Humans & then used as a chainsaw is normally used, slicing through the Daemons. All around is carnage, just as you start to bond with a character they are skewered, flung aloft, then tossed aside like so much garbage & these are the lucky ones. But it's done with so much warm humour, such zest, even as the character you really liked is being chased by a Daemon, you're turning the page, half to see if they escape, half to see how they get killed.
This book is just funny, and has been described as a gothic horror story for the 21'st century, also as satirical, gripping and highly entertaining. But more to the point this book is just fun, the old-fashioned gut bursting, tear jerking laugh out loud fun.
Slight spoiler, there's a lovely twist at the end.