David Steinberger, president and CEO of Comixology, Amazon’s digital comics marketplace, is leaving the groundbreaking online platform he cofounded with plans to direct a new Amazon-wide initiative. Tom Ashley, head of product UX and subscriptions at Comixology, and Jeff DiBartolomeo, chief technology officer at Comixology, will take over the management of Comixology, which was acquired by Amazon in 2014, going forward.

Steinberger announced his departure from Comixology via a five-part note posted on Twitter, in which he confirmed that he will continue to be an advisor to Comixology. And while Steinberger called his departure “a tough decision,” he emphasized that his role directing a new Amazon-wide initiative “is too good an opportunity to not take,” adding: “I’m ready for a new entrepreneurial challenge.”

Steinberger is leaving Comixology as the entity goes through a final—and somewhat bumpy— integration of its services, features, shopping technology, and consumer base into the Amazon platform. The process has resulted in some confusion and complaints from comics consumers, who are used to having a standalone digital platform focused on the sometimes arcane needs of comic book fans.

Comixology was founded in 2007 by Steinberger, John Roberts, and Peter Jaffe. Under Steinberger’s leadership, Comixology has grown into the dominant marketplace for buying digital comics of all kinds, expanding its reach into foreign comics in English and Japanese manga. The service also launched a digital comics self-publishing service, Comixology Submit (which has since been integrated into Kindle Digital Publishing), and a digital comics subscription service, Comixology Unlimited, and publishes original digital comics and graphic novels via its Comixology Originals imprint, which also publishes print graphic novels via such partners as Dark Horse Comics.

Steinberger is well regarded throughout the comics industry, both for his personal style and for an entrepreneurial vision of digital comics and how to integrate the format into a world of print publishing and retailing. In an interview from 2012, Steinberger told PW: “We’re comic book people. We’re concentrated on making a great experience for comic books in digital.”

Indeed, at one point early in its existence, Comixology was seen as a serious threat to physical comics shops. However, since then, digital comics have helped broaden the market for comics reading overall, sending consumers into both comics shops and bookstores in search of print.

In his Twitter post, Steinberger said: “I’m extremely confident in Jeff and Tom, the rest of the Comixology leadership team, and the many passionate, comics-loving employees that strive day-in & day-out to make everyone on the planet lifelong fans. To all Comixologists: I’ve learned so much from you. Thank you.”