Donald J. Sobol, who created the book series featuring child sleuth Leroy "Encyclopedia" Brown, has died at age 87.

Sobol's books were popular with a generation of kids, beginning in the early 1960s, because they portrayed youngsters who were wise beyond their years and could solve problems that baffled adults. That genre, championing a wisened, daring youngster, harkens back to earlier literary heroes such as The Hardy Boys and Nancy Drew. And the titles of come Encyclopedia Brown books -- involving the Case of the Midnight Visitor or the Case of the Secret Pitch -- echoes those forerunners, as well.

According to the AP obit, the concept — in which the solutions to the mysteries are shown after the story — came to Sobol while he was researching an article at the New York Public Library, and a clerk mistakenly handed him a game book, with puzzles on one side and the solutions on the other.