by Nicholas Pileggi. Simon & Schuster, $17.95. Mr. Pileggi has succeeded in extracting what amounts to a lively oral autobiography from a Mafia factotum who is now, thanks to his decision to turn state’s evidence, living in prosperous anonymity at public expense. Aside from the predictable elements of bloodshed and conspiracy, the book is interesting and discouraging for what it reveals about corruption among public officials, union officials, policemen, and prison guards. Is anybody, one wonders, not on the take? And all bought cheaply, too.