A few "inland" recs:
As has been mentioned, Slate’s in Hallowell is closed temporarily.
Also in Hallowell (just south of Augusta on Rte 201) is Liberal Cup, exceptional brewpub, Cafe de Bangkok (Thai), and Hattie’s Chowder House (great Lobster stew).
If you’re into diner history/architecture there is A-1 Diner in Gardiner.
I disagree about Margarita’s…very ordinary Americanized Mex.
Other ideas: Montsweag’s Roadhouse in Woolwich (Rte 1 just south of Wiscasset) for steaks/burgers, Bombay Majal in Brunswick (Indian), Camino Real in Brunswick for Cali-style Mexican.