The Anomaly: Book 1 of The Anomaly Files by Michael Rutger (Ex-Library HC/DJ)
Not all secrets are meant to be found. Nolan Moore is a rogue archaeologist hosting a documentary series derisively dismissed by the "real" experts, but beloved of conspiracy theorists. Nolan sets out to retrace the steps of an explorer from 1909 who claimed to have discovered a mysterious cavern high up in the ancient rock of the Grand Canyon. And, for once, he may have actually found what he seeks. Then the trip takes a nasty turn, and the cave begins turning against them in mysterious ways. Nolan's story becomes one of survival against seemingly impossible odds. The only way out is to answer a series of intriguing questions: What is this strange cave? How has it remained hidden for so long? And what secret does it conceal that made its last visitors attempt to seal it forever?