“Picking a finite number of campgrounds to include in a ‘best of’ listing is not an exact science. Are 25 too few, are 100 too many? More important, I feel, is that the criteria remain constant and based on unchanging standards that the author can share with the reader.”

So writes guidebook author Tom Watson in the preface of “Best Tent Camping: Minnesota,” just updated in a third edition from Menasha Ridge Press.

Order is Watson’s modus operandi; he is all about the details. He rates his top 50 campgrounds in the state (just one private) on criteria such as beauty, security, levels of quiet and privacy, cleanliness and spaciousness. Then, he ranks each of those categories from “ideal” to “acceptable.” He also assigns the best among his list for birding, for hiking, for boating, for families — you get the idea.

Watson has been busy: The fourth edition of “60 Hikes within 60 Miles: Minneapolis and St. Paul” also was released in May. He has a third guidebook, “Best Minnesota Camper Cabins.” Find them in the metro at Midwest Mountaineering, Barnes & Noble, and Bibelot shops.