In the mystery genre, the one characteristic that the enduring figures of Sherlock Holmes, Nancy Drew, and Encyclopedia Brown have in common is a rational mind. The source of their strength is their ability to think and think well. A study examined some typical examples of the mystery genre in young adult literature and surveyed children and adults regarding their enjoyment of mysteries. Two sets of questionnaires were developed. In the first set, 32 adults and 29 children responded to a long questionnaire distributed through Bennington College (Vermont) students to a random set of adults and children. The second questionnaire was a condensed version, rewritten for 79 fifth- and sixth-grade children at a Bennington public elementary school and specifically addressing questions about Sherlock Holmes, Nancy Drew, and Encyclopedia Brown. Results indicated that: (1) children gave suspense as the reason they liked mysteries, while adults focused on escapism as the appeal; (2) children ranked bravery and risk-taking as important qualities about detectives, while intelligence ranked highest for adults; (3) males preferred male detectives, while females preferred either female detectives or mixed pairs; and (4) the "Goosebump" series (in which the irrational and the supernatural create disorder and fear) was chosen by 71% of the girls and 35% of the boys as their favorite mysteries. Results also indicated that children selected mysteries based on the cover and the publisher's "blurb." Over the years, the covers of Nancy Drew mysteries and Encyclopedia Brown mysteries have changed to reflect changing styles and attitudes. (The survey instruments are attached. Contains 16 references.) (RS)