LaBeouf was most recently seen in "Eagle Eye." He had previously starred in the blockbusters "Indiana Jones and the Kingdom of the Crystal Skull," "Transformers" and "Disturbia."

Grisham's novels "The Firm," "The Client," "A Time to Kill" and "Runaway Jury" have been made into successful films.

Variety.com said LaBeouf has signed on to star in the movie version of "The Associate," playing a young man about to graduate from Yale Law School who is manipulated into taking a position at a firm and given privileged information about a multibillion-dollar lawsuit.

The novel is to be published next month, the entertainment industry trade newspaper said.