THE BONE LABYRINTH is book 11 in James Rollins Sigma Force series. The books can be read separately, but it can be easier to understand the story and the characters past stories if you have read the previous books.

A discovery in a cave in the mountains of Croatia could hold the answers to, or rather a clue, to the mystery of what anthropologists calls The Great Leap forward, the sudden outburst of intelligence that happened 50,000 yeas ago. No one can explain why the homo sapiens suddenly become smart and started to invent things. Not until now.

But, the group of scientists that are investigating a cave in Croatia is suddenly attacked by unknown foes. There are those in the world after this knowledge for themselves that will not stop at anything to get what they want. Commander Gray Pierce leads a team to Croatia to see if they can be to any help after the attack. Will they arrive in time?

Back in America Joe Kowalski and Monk Kokkalis are trying to find out more about the caves in Croatia by questioning Maria Crandall, whose twin sister Lisa is one of the scientists investigating the cave. Could Maria and Lisa's research on exploring the origin of human intelligence be behind the attack in Croatia? And, who is after the knowledge and for what purpose?

THE BONE LABYRINTH is a breathtaking thriller, which takes us to Croatia, China, and South America in the hunt for answers. I liked every minute of the story, but I especially like Joe Kowalski's storyline. He and scientist Maria Crandall are kidnapped and taken to China together with Baako a young gorilla she has been raising. I also like Seichan, Gray Pierce girlfriend is back after being absent in the last book. It's good to have her back since she is quite forceful and handy to have in a fight.

The story is intriguing, and I love the mix of science and adventure Rollins so often manage to combine so well. I was pulled into the story, and I read this book with so much wonderment. THE BONE LABYRINTH was never boring, and I think this is a perfect book for anyone who loves to read adventures. I found it hard to stop reading after I had started. And, I actually cried at the end of THE BONE LABYRINTH. Not just teary-eyed, I actually cried. It is such a bittersweet ending.