Another Kind of Monday

When Mark, a Pittsburgh high school senior, is assigned Great Expectations for holiday reading, he checks out a library copy-which happens to hold three crisp $100 bills and an anonymous note inviting the finder on a secret treasure hunt that promises even greater riches. This intriguing premise leads to some suspenseful, first-rate clue-cracking, as Mark solves the riddles in a series of cryptic notes. Each involves delving into colorful, curious pieces of Pittsburgh history. But Cole (coauthor of Funnybone) periodically downshifts as Mark's journey becomes one of self-discovery, and the momentum of the quest suffers, along with the story itself. His relationship with Zeena, a teenager of mixed race whom he chooses as his fellow ""quester,"" evolves from friendship to romance; they share similar family-related problems, which are more or less resolved through insights gained from each other's perspective. These developments seem secondary, however, as do issues of race and feminism that surface in fairly broad, familiar terms. The answer to the final riddle, an attempt to tie together both strands-the quest of ""great expectations"" and the inner journey-proves a letdown in an otherwise imaginatively conceived plot. Ages 12-up. (Apr.)