Shari Lewis has a TV program for children. This is a collection of the letters that have been sent by her audience. The book makes a fine advertisement for the program. However, since advertising generally comes free, it doesn't seem reasonable to expect anybody to plunk out $2.95 to cudgel their own senses -- but wait!! On the back of the jacket is word of the publisher's ""Dear Shari"" contest Attached to each book is an entry blank inviting parents to send in their children's unny remarks and letters. The best 100 entries will receive two Shari Lewis puppets and some of them will be immortalized in Miss Lewis' next book. To ensure winning, contestant parents should be advised that the awkward letter appears to be favored n the evidence of this book -- the gamut of the naive bit; misspelled, ungrammatical, irrelevant or impertinent. The readership's smile is guaranteed to set like cement. WHAT HATH ART LINKLETTER WROUGHT!