Camino Island by John Grisham is my first favorite book of the year. Although a little different story line from his usual lawyer related books (no courtroom drama), Camino Island is just as thrilling and mysterious and a little reminiscent of The Thomas Crown Affair.
From the cover:
A gang of thieves stage a daring heist from a secure vault deep below Princeton University's Firestone Library. Their loot is priceless, but Princeton has insured it for twenty-five million dollars. Bruce Cable owns a popular bookstore in the sleepy resort town of Santa Rosa on Camino Island in Florida. He makes his real money, though, as a prominent dealer in rare books.
Mercer Mann is a young novelist with a severe case of writer's block who has recently been laid off from her teaching position. She is approached by an elegant, mysterious woman working for an even more mysteries company. A generous offer of money convinces Mercer to go undercover and infiltrate Bruce Cable's circle of literary friends, ideally getting close enough to him to learn his secrets.