Shangri-La by Christopher Cartwright (Sam Reilly #21)

 The story starts with a plane that is hit by lightning and goes down. The lone survivor finds his way to the mystical land of Shangri-La. As it happens, the survivor is the future author, James Hilton of Lost Horizon. Adventurer Sam Reilly is tasked to find the ancient sanctuary to save it from an ancient struggle that will determine the existence of mankind.

The story is fast-paced and wildly imaginative. It has a real Indiana Jones feel and deals with ancient mysteries. A ton of action and suspense.