For quick and dirty inspiration, you can't beat children's books. Here are a couple that might make good Cryptworld scenarios:
Justin Richards, The Invisible Detective: Shadow Beast, 2003
Something is killing pets, and maybe people, in the sewers of 1930s London. Meanwhile, thieves have tunneled in to a bank vault, ripping apart barred gates with seemingly superhuman strength but leaving expensive valuables behind. Art Drake, 14-year-old son of a police inspector, and his friends investigate. Seventy years later, Drake's grandson encounters similar mysteries in modern London. Parallel mysteries running decades apart; not sure how you would do that in a game, but the two story lines complement and feed off each other.
Andrea Beaty, Attack of the Fluffy Bunnies, 2012
I've mentioned this one before. It is a spoof of monster movie cliches but again we have youthful protagonists up against genuinely challenging if goofy creatures from beyond. Kids stuck at isolated summer camp? Check. A "meteor" falls nearby? Check. Adult camp counselors disappear then return acting strangely? Check. Fellow campers disappear, period? Check. The fact that the protagonists are monster movie buffs adds to the fun.
Any short reads you think would fit the bill? (No, Stephen King's Cycle of the Werewolf aka Silver Bullet is not a children's book! )