I try to keep up with novels with a cryptozoological influence. That's very hard now with so many self-published and Web-published novels, most of them awful. Predator X looked interesting, though, and mainly it was. It kept my attention, though the cryptozoology isn't the focus of the novel. Author Waller writes well and has avoided the bloat afflicting novels these days and kept it short (149 pages). Actually, the novel is a little too short: none of the characters has any backstory, and the explanation of how the caving team this novel focuses on ended up in its situation needs more development. There are a couple of good plot twists, especially at the very end. Predator X (a giant pliosaur) isn't the focus here: it exists and is important to the plot, but isn't the focus of the novel, which deals more with extraterrestrial activities and a creature which reminded me of Dean Koontz' antagonist in the novel Phantoms crossed with the one in the movie The Thing (John Carpenter version). There are a few factual errors (e.g., you wouldn't find trilobite fossils in Jurassic sediments) and the ecosystem in a deep underground sea doesn't really work, or at least isn't adequately explained. (Read Warren Fahy's Pandemonium for a much better attempt at this.) I should be fair, though, and note the ecosystem isn't entirely natural: someone's been customizing it, so to speak.
In sum, Predator X isn't a great novel, but it's a fun way to pass a couple of hours.