It's a fabulous town to eat. Some of the eating areas that we have found:
By the Château
There aren't many options here but the views can be worth the effort of finding a good restaurant.There is one on the road looking out over the Loire and - inevitably - you can eat in the castle grounds - although I think it's expensive for what you get. The view is superb and it would be a good place to take a picnic.
The old town
This is behind the main street, heading towards the chÃ¢teau - ask for Place St Pierre. If you enter the town from the north there are plenty of parking spaces along the Loire to the left (behind the Marie) and it's only a short walk from there to the old town.
There are a number of excellent restaurants around the square (in front of the old church) but be careful: some of them are very expensive and offer little more than cheaper ones. Also, don't settle too quickly for the obvious ones: some of the smaller establishments and out-of-the-way places are worth considering. In particular, in one of the side streets, there is an Indian restaurant like no other that I have ever eaten in and well worth a visit.
On and around the Main road
The restaurants along the main road are probably less adventurous and less value for money. They can also be very busy and involve long waits for your food. They are an easy option, though, and very convenient for shopping.
Rue St Nicolas
Try some of the streets off to the left as you walk with your back to the Loire - that is, to your left as you face the Loire. In particular, there are a lot of interesting places on rue St Nicolas and the streets off it.