Things to look for when choosing a guidebook:

• The year it was published.
  Make sure to get the lastest edition whenever possible for the most up to date info. Check the first few pages to see what year it was published.

• Countries it covers.
  Make a list of where you are planning to visit then check to see that your guidebook covers these.

• A book specific for your destination.
  If you are only going to Paris, get a Paris book, rather than a France book. The more specific, the more information that will be of use to your trip.

• The style of travel.
  If you are a budget backpacker planning on staying in hostels or cheap hotels, you will need a different style of guidebook than someone looking for a more high end trip.

• Does it have what you are looking for?
  I use my guidebooks mostly for the accommodation listings and the maps, so I look for a book with lots of accommodations listed and clear maps. Some people use them for the history of sights. Decide what you will be using it the most for, the concentrate on that.

Backpacking or Budget Travel:
Lonely Planet
Lets Go
Rough Guide
Rick Steves

B&B / Hotel style travel:
Eyewitness Travel Guides
Fodors
Frommers

With Kids:
Take Your Kids to Europe.
Fodor's Around Paris With Kids.

Before You Go: :
First-Time Europe: A Rough Guide Special
Rick Steves' Europe Planning Map