If there is one attraction in the Loire Valley that can compete with the châteaux, it's places to eat (and, of course, drink the great wines of France). We'd like to recommend restaurants that we have found agreeable but we are very aware that food and ambiance can be a very personal thing: what one person enjoys, another finds irritating. Also, restaurants and bars have a habit of changing hands fairly regularly, and our experience may rapidly become out of date.
So, our recommendation is: experiment. If you want to be as sure as you can and you can afford the prices, then it's a good idea to use an established guide to restaurants, such as the Michelin guide - but you will almost certainly pay for the experience and may be missing some great places that aren't on the guide books' radar.
Another suggestion is to go where others are eating (and obviously enjoying it). If you do that, listen out for French voices, too: if they eat there, it's likely to be good. But remember: you may find the menu contains things that are a challenge for you to eat.
All the restaurants will have a menu outside, so check that you like what they serve. If you're not so keen on sea food, for example, check it out first.