The distinction here is between things you can measure (less) and things you can count (fewer)…Regrettably, less used incorrectly in place of fewer is so common nowadays that for many people fewer has come to sound stilted, even if they sense that it's correct. Hence, those grocery store express-lane signs that say "15 Items or Less" instead of "15 items or fewer."
Imitate vs. emulate, that vs. which, pliant vs. pliable, immigrate vs. emigrate…when it comes to the English language's maddening nuances, sometimes even the most passionate word lovers need a refresher course. Sort out the intricacies of hundreds of synonyms and homonyms with this thesaurus/usage manual, an alphabetical listing from "a, an" to "your, you're, yore" that educates and entertains in equal measure! (KG)