Google Inc. is in the final stages of launching its long-awaited e-book retailing venture, Google Editions, a move that could shake up the way digital books are sold.

The long-delayed venture—Google executives had said they hoped to launch this summer—recently has cleared several technical and legal hurdles, people close to the company say. It is set to debut in the U.S. by the end of the year and internationally in the first quarter of next year, said Scott Dougall, a Google product management director.

In...