If all of the tales told by newspapermen about their craft were laid end to end, they would reach from Los Angeles to downtown Manhattan. Wring out everything but the truth, and they'd reach from Los Angeles to Whittier. So, laying aside all claims of truth, longtime newspaperman Jack Donahue brings us dowdy-but-enterprising Hack Donavon of the Press and the Purification of Houston (Shearer: $9.95). What's a crafty reporter to do in 1950s Houston to humble the two rival papers, clean up his town and ingratiate himself with the wealthy widow, Millicent Durham? Why, he finds himself an obscure and naive county constable, who is also a full-blooded Navajo, and puts him on the warpath against Houston's corruption. A rollicking, funny novel inhabited by the zaniest cast since "Front Page."