The Deacons' Testament, which will be on the newsstands on June 5,is expected to sell like 5c cigars when people learn that it uncovers the true story behind Snooperman, the mysterious genius who has reversed more than 100,000 books during his brilliant career. The Testament has all the dope--pictures of Snooperman in the act, a full story of how libraries hermetically sealed were broken into, and an editorial entitle. "What are we going to do about it?" Dick Lane, the editor, with a loyal staff of underlings, has seen to it that the Testament has complete coverage of all events during the year.