On his first few albums, George Thorogood played rocky blues with so much enthusiasm that it was easy to overlook his limited talent. With Boogie People, his ninth release, the musical lode he so tirelessly mined seems to have gone drier than dry. His slide-guitar solos all seem the same, and his rasp of a singing voice, with its tiny range, is little more than an affectless monotone. Except for Thorogood's anemic, out-of-tune stab at a country tune, ''Oklahoma Sweetheart,'' this album is barely distinguishable from his earlier work. But the low point comes on ''No Place to Go,'' when he tries to emulate blues great Howlin' Wolf, but produces more of a moo than a howl. Thorogood has clearly listened to the right people, but unfortunately he can't make music with his ears.