The updated app will feature a simpler interface and a new tab specifically for audio books and is set to be released in the coming months, Bloomberg reported, citing sources familiar with the development.
In December Apple hired Kashif Zafar, former senior vice president with Amazon's audio book unit Audible, to lead the effort.
The renewed effort in iBooks seems to be an attempt to regain market share in e-book services. Apple was once a bigger player in the space, but was fined in 2016 by the U.S. Department of Justice for conspiring with publishers to raise e-book prices.
Apple did not immediately respond to a request for comment.