Approximately 18 months after its launch, Amazon Upgrade boasts more than 100,000 titles, and the company is starting to expand the program beyond the group of professional publishers that have formed the core of its first participants. “We’d love to have more books, and we’re working with publishers to add more titles,” said Laura Porco, director of Upgrade.

Under the program, customers who have purchased a print edition of a book can get unlimited online access to it for an additional charge of 10%—20% of the least expensive price of the title. Amazon splits the extra revenue with publishers.

John Wiley, McGraw-Hill and Pearson are among the publishers that have supplied the most titles to Upgrade, Porco said. No publisher wanted to comment on the record about its Upgrade experience, but the consensus was that Upgrade has been successful in generating incremental income. According to Porco, no publisher has pulled its titles out of Upgrade.

Some publishers that are considering putting titles in the program expressed concerns about the financial model, though that didn’t appear to be a dealbreaker. Jeremy Ross, editorial director of Tokyopop, said he would prefer to see a stand-alone price for Upgrade rather than a sliding scale. Still, Tokyopop is in discussions to add some titles to Upgrade, and Ross sees the program as a great way to begin to get consumers accustomed to paying for online content. While the online functionality offered by Upgrade would seem to make it more valuable to readers of nonfiction titles, Ross believes fans of Tokyopop’s fiction titles will appreciate online extras such as searchability and bookmarking. “As long as there are extra benefits, consumers will pay a little extra,” Ross said.