Google, the Authors Guild and the AAP maintain that the proposed settlement will be beneficial to authors, publishers and readers by making it easier to find, distribute and purchase books, especially those that are out of print.

However, critics have raised several objections, including what they perceive as excessive control by Google over prices and over so-called "orphan works." The latter are books that are under copyright but whose owners can't be found because the author has died or the publishing house disappeared.

The court where the case is being heard allowed hundreds of backers and critics of the proposed agreement to submit opinions for several months. That comment period closed earlier this month.