Books: Back to the Riffraff
SWEET THURSDAY (273 pp.)John SteinbeckViking ($3.50). John Steinbeck respects the underdog, but he melts uncontrollably before a no-good, boozed-up bum. His sentimental eulogies of riffraff began with his first successful book. Tortilla Flat (1935), continued in Cannery Row (1945), and appear again in Sweet Thursday, which is really a return visit to Cannery Row. It