Any summary of The Tiger Warrior, marine archaeologist David Gibbins’ fourth thriller featuring Jack Howard (also a marine archaeologist), will inevitably make the book sound more exciting than it actually is. The story centres on a pair of gems stolen from the legendary tomb of Qin Shi Huang, the first Chinese emperor, which, when returned to Huang’s resting place, will grant the gift of immortality.

The novel begins with a pair of Roman legionnaries robbing the gems from a Chinese thief and beginning a journey along the Silk Road, the trade route that connected ancient Rome with China.

In the present, the “Tiger Warrior” of the title is a veteran sniper, the newest member of an ancient Chinese sect that has lasted for 66 generations. Ordered to kill Jack, he’s given only one scene. Moreover, the sect’s leader, a supposedly colourful megalomaniac who built a replica of Emperor Huang’s tomb in his headquarters, is never seen.

Gibbins’ characters rarely just talk. Instead, they spout research, and the bulk of the novel features one explorer after another providing explanations so that readers understand what’s going on. In The Da Vinci Code, Dan Brown at least had the sense to include something interesting – self-mutilation, a narrow escape – in every chapter, whereas Gibbins includes a scant half-dozen action sequences, most of them two pages or less, all followed by more research.

In a good adventure novel, the goal is secondary to the action. In The Tiger Warrior, the goal is the action. So much of the book is devoted to characters explaining the background to Gibbins’ supposedly thrilling plotline, there’s little left that actually thrills.