Because this one's a guide to ""over 400. . . great inexpensive regional restaurants--all within 10 miles of a major highway,"" it's difficult to assess: unless you've been on the road as much as the peripatetic authors, most of these places will be unfamiliar, and they are to us. But the Sterns' candor in describing two iffy spots that we do know--one excused its ""quaintness,"" the other its gimmickry--inspires confidence in their enthusiasms. Like Calvin Trillin, they're food buffs but not food snobs, appreciative of fresh ingredients, local specialties, no-nonsense service, and ""a real cook in the kitchen."" They're obviously kitchen-wise too, and they'll as soon tell you what to skip--and why--as what to eat. No oversell here altogether: ""We're happy when we can find decent food and a smiling face anywhere in North Dakota,"" begins their encomium to Zacher's Cafe and its disguised (as ""pigs in blankets"") holubsti. A non-plastic tribute to non-plastic food.