Whilst Lonely Planet Guides - and their various knock-offs - tell you the basics of travelling to the places you think you'd like to go to, DP tells you all about the places you really don't want to go to, what to do when you get there, and how to come back in one piece. Written by a motley collection of adventurers and war correspondents (who have a terrifying attrition rate - at least two contributors to previous editions are now dead) DP is not only a guide book to war zones and danger, but also an excellent grounding in the geopolitical realities of how those places got like that, and a guidebook to surviving the travails and difficulties of being a western traveller in the Thrid World.
Where else would you find chapters on how to survive being kidnapped by Columbian drug barons, bribing thrid world police offers, and how to avoid landmines? Even the list of things to take travelling with you differs from teh usual advice - along with the same old/same old tips on travelling light and taking torches and waterproofs, you're advised to take gifts for the people you meet - cigarettes, and a large supply of cheap watches.
As travel advice, it's excellent. As a geopolitical primer, it's the best single book I've ever read. As a book of stories of people travelling to places and meeting people you'd never want to, it's great fun. What reason is there not to own a copy? I'll be sending copies to many of my friends this Christmas.