I'm a food tourist. For finding restaurants in Europe, the Michelin Guide Rouge is information perfection. Complete data on a country's good hotels and restaurants, the red guide is truly all you need.
Best as a book, it is also searchable online. The design is fantastically dense. The German guide, for instance, is 1500 onionskin pages in a handbook size. There's a bit of information about each town, including excellent small maps for bigger towns and a line or two about major tourist destinations. Each restaurant or hotel then gets about 8 lines wherein you will find packed the name, location, contact information, hours, prices, and a couple of descriptive lines of text.
The most important thing is the listing's icons. Restaurants get 1 to 5 forks. But it's not just a 1-5 scale. If the forks are red then the place is a "pleasant restaurant", a uniquely comfortable dining room. Rare places have the valuable Michelin stars that indicate excellent service and comfort. And there's the "bib gourmand" for inexpensive places. That makes for four dimensions all for a quick scan.
The editorial quality of the reviews is fantastic (despite some recent controversy). Anything that's even in the guide will be a good meal; to my American tastes 2 forks and up is a fine restaurant. These ratings are given by serious food people, much more useful than the crappy guidance from Fodor's or Frommer's.
My most fervent wish is we could have a Red Guide for the USA. Alas, I think we just don't have the quality or culture to deserve it. Zagat is the closest we have, and it's just not the same maturity. And so peculiarly democratic!