The inside is nicely decorated, including this collection of old tins. Besides burgers and sandwiches (try the egg salad), they offer soup and salads. The home-made pie is worth checking out. Probably not where you'll want to eat on your way to Seattle, but on the trip home it can be an attractive option if you're too hungry to wait until you get to Pullman to eat. But you may have to wait a bit for your food: the service isn't especially fast.
Back on the highway you'll climb up a long grade far above the lowlands you've been winding through for some of the most boring driving of the trip. The road undulates up and down along the hills, but at least it goes straight most of the time.