This is probably Preston's best thriller as a soloist and it improves on the Codex of which it is loosely a sequel to.  The tie-in being that the main character is Tom Broadbent who was one of the brothers that Preston introduced in his earlier book.  Broadbent happens across a man who has just been shot by a long range assassin in a gorge in New Mexico.  With the man's dying breath he hands Broadbent a notebook that he tells Tom to give to his daughter and promise not to give it to the police.  Tom then leaves to get the police to show the body (but not the notebook).

In the meantime the assassin (Maddox) has come to the dead man to look for the notebook but finds only a "treasure map" and a weird fossilized rock.  He hides the body and goes back to New York with what he found.  It turns out he is an ex-con that was sprung from prison to trail the dead man specifically to get his notebook by Ian Corvis, who works at the Museum of Natural History (where is Special Agent Pendergast?).  Corvis is upset that Maddox did not get the notebook but is fascinated by the fossil, which he gives to his research assistant to run tests on.  Maddox learns in the paper that Tom Broadbent was the person who discovered the dead man and he figures that Broadbent has the notebook and he returns to New Mexico to get Broadbent.

In the meantime, the police think that maybe it was Broadbent who murdered the man and he is their prime suspect.  Preston does a marvelous job of weaving a lot of tense moments into the plot and keeping the audience constantly guessing.  There is a teaser about moon rocks in the beginning of the story that seems significant but the story seems to hedge on the hunt for a "preserved" dinosaur and the reader wonders what it has to do with the moon rocks.  Preston does a marvelous job of tying everything together.

The plot rolls along with Broadbent's wife being kidnapped by Maddox, the police hunting Broadbent and a covert special government agency sending in commandos to possibly kill everybody.  An excellent job by Preston!  I didn't give it the full five stars because some things towards the end of the book left me shaking my head as to the plausibility.