ECCENTRIC CIRCLES: Around America in a House on Wheels by Richard B. McAdoo (Houghton Mifflin: $19.95; 337 pp.). The trouble with many travel books is that authors often read too much into the journey--the places visited become symbolic, artfully re-arranged to imply a voyage of discovery. "Eccentric Circles" has the opposite problem, for it reads too frequently like a compendium of facts derived from travel brochures. It's generally well written--the title promises as much--but Richard B. McAdoo, for years an executive with Houghton Mifflin, hasn't sorted out the interesting adventures from the pedestrian, nor emphasized the special nature of mobile-home travel. Case in point: Near Bozeman, Mont., McAdoo and his wife encounter scores of Airstream RV owners gathering for an international rally (3,600 will show up eventually), yet didn't stick around to ask questions, make contrasts, re-examine stereotypes. McAdoo's passivity ensures that he relates banal impressions that serve mostly to highlight his own, admitted New England biases: The South is hospitable and racist, the Northwest progressive, Texas big and big-spending.