The head of the book publishing industry's trade group is stepping down.

The Association of American Publishers announced Monday that Tom Allen, a former Maine congressman, will leave early next year. He has served as CEO of the association since 2009, presiding during a time of rapid growth of electronic books and conflict between publishers and the leading seller of digital works, Amazon.com.

Allen, 71, said in a statement that after 20 years of commuting to Washington he looked forward to returning to Maine and focusing on part-time and "mostly voluntary activities" such as writing and environmental conservation.

No successor to Allen has been named, but the association said a search is underway.