Having established himself in Twixt Twelve and Twenty as the spiritual and ethical mentor of today's groping youth, Pat Boone, crooner par excellence, once more sings a song of propriety. The theme, again, is proper behavior, the embellishments, a series of admonitions on the evils of cheating, indiscriminate kissing, laziness, moral laxity, and lack of faith. Loosely woven together and accompanied by cheery little anecdotes which deal with the author's personal observations--somewhat bland--the message is revealed with verve. It is evident that Mr. Boone approaches his subject with sincerity. But his approach, reminiscent of Elsie Dinsmore, just might, with its irritating complacence of tone, turn all but the conformists toward rebellion. Mr. Boone is a good singer, a charming actor, but between you, me and the gatepost, it is fortunate that the fabric of American teen age morality does not depend wholly on his design.