When we were traveling around Italy on our honeymoon, Fred Plotkin's: Italy for the Gourmet Traveler was our bible. Encompassing all of Italy, it covers bakeries, markets, wine bars, restaurants of all price ranges, local cheese shops, regional culinary specialties, and so much more. If you are traveling to Italy and want to eat your way through, I seriously recommend you buy this book. It's hefty, but you'll be so happy you packed it.
I have been searching for a similar guide for Paris and was not having any luck until I came upon Clotilde Dusoulier's new guide: Clotilde's Edible Adventures in Paris. If you are not familiar with Clotilde, she is the author of one of my favorite blogs, Chocolate & Zucchini.
And if there is one thing this girl knows, it's food. The new book is organized by arrondissements cataloguing her favorite bakeries, restaurants, ice cream shops, chocolate stores, cheese shops, cafes, bars, and markets. She even gives tips for French etiquette and ordering. The best part is that you are getting advice from a true Parisian who loves food. C'est bon!