Cryptids are fascinating and not covered much in YA literature. There's Smith's Cryptid Hunters (2005), Zindel's Loch (1994)and Savage's new Nessie Quest, but there is room for many more titles like this.
Thanks to Key's powerfully descriptive language, I never, ever want to spend time in Florida swamps, but his books are HUGELY popular in my library and have a stalwart band of followers who read everything he has written. The fact that his books are all stand alones is fantastic. Every time I see a new one is being published, I feel a wave of relief that I have a new book to hand to students that doesn't require them to commit to eight books!