The area around the palace and Marktplatz has the best concentration of restaurants. Regional Swabian cooking — Maultaschen (stuffed pasta parcels), Spätzle, Zwiebelrostbraten (roast beef with onions) — is well represented across price ranges.
Schlosstüble in the Schloss Hotel, about a block from the palace, is a reliable choice for traditional German and international cooking in an ornate 19th-century room. The Red Room, with its carved wooden ceiling and baroque detailing, is over the top in a very deliberate way. Schnitzel with Spätzle is the thing to order.
Alte Sonne offers contemporary German cooking with a stylish interior — more modern in feel than the palace-adjacent places, and a good option if you want something less heavy.
Ratskeller Café on Marktplatz has outdoor seating and does a good breakfast and brunch. It's a local institution rather than a tourist trap, and the lunch prices are reasonable.
Goldener Pflug on the west end of town doubles as a hotel. The wine list is serious and the food is carefully plated — good for a proper dinner if you're staying overnight.
The castle terrace restaurant operates in summer with live music in the evenings; it's a tourist-oriented but pleasant spot for lunch with a view of the baroque gardens.