Whether he’s in L.A. with Easy Rawlins or Manhattan with Leonid McGill, Walter Mosley delivers some fine books. Bob Moyer has a great time with the latest. Reviewed by Robert P. Moyer AND SOMETIMES I WONDER ABOUT YOU. By Walter Mosley. Doubleday. 272 ages $26.95. What’s happened to the gunsels, the dames, the twists, the…