SCRIBD RAISES $22M FOR ITS SUBSCRIPTION E-BOOK SERVICE.

Scribd, a company offering unlimited access to half a million e-books for $8.99 a month, is reporting that it has raised $22 million in additional funding.

The round was led by Khosla Ventures, with Khosla partner Keith Rabois previously an executive at PayPal, LinkedIn, Slide and Square joining the Scribd's board as an observer. Asked via email about how the subscription business will pay out for books, Rabois noted that model has already changed the way we consume other forms content.

''With over 80 million users in nearly every country, the Scribd team is well positioned to develop to a big global audience,'' he said.

Started in 2007 and incubated at Y Combinator, Scribd started out as a document sharing service. While it still supports those features, its focus shifted last year to subscription e-books, where competitors include startup Oyster and Amazon's Kindle Unlimited service.

Echoing Rabois'comment, co-founder and CEO Trip Adler told me that Scribd now reaches more that 80 million unique visitors each month. He didn't specify how many of those visitors are actually paying subscribers, but he did say subscriptions have been developing an average of 31 percent each month since the service was formally revealed in October 2013.

Just a couple of month ago, the company also grew into audiobooks, and Alder said the response ''beat our expectations''. Users have already logged 180,000 listening hours, according to Scribd.

This brings Scribd's funding to $48 million. Previous backers Redpoint ventures, Charles River Ventures, and Silicon Valley Bank also invested in the new round.

Adler said he plans to spend the money on developing the product with a focus on algorithmic book recommendations and the reading experience itself, as well as continuing to grow the content available in Scribd.

He also interpreted a comment he'd made, when he said he was ''not ruling out'' a tiered pricing model in the future. It sounds like I may have explained that as a more definite plan than it really was when I brought it up earlier this week, Adler said, ''I think I was just brainstorming with you there. We are still focused on the $8.99 price point and there are no plans to change it''.