Gr 3-6 This newest installment in the ``Encyclopedia Brown'' series begins with a mystery that involves an invisible ray gun and a nest of baby birds and then offers a potpourri of strange-but-true happenings in the outdoors. The book is divided into seven sections with titles such as ``How to Catch `Em Without Hardly Trying''fish stories with one bird story thrown inand ``Man's Best Friends, Usually''about birds, a monkey, and a snake. These stories from Encyclopedia's scrapbook should delight young readers. The book will appeal to Encyclopedia Brown fans, and it will also attract the attention of nature enthusiasts. Beverly Maffei, Horace Mann School, Melrose, Mass.