Hollywood writers are so out of touch with mainstream America that they are incapable of creating new story lines that have broad appeal. In order to pay the bills, they must cinematize classic stories (JRR Tolkien's Lord of the Rings), rehash old heros (Master and Commander is really a Horatio Hornblower remake), or remake past hits (Rat Race).
Literary adaptations have been a part of the film world since it began at the turn of the century.
Master and Commander was based on books by Patrick O'Brian.
The Hornblower series was written by C.S. Forrester.