Scribd, a digital document sharing service, is launching an online retail market for books and documents on Monday, betting that a surge in interest in reading online will help it transform into an Ebay or an Amazon.com of text.

The two-year-old Silicon Valley start-up, whose doubling of audience size every six months has been compared to YouTube’s explosive growth, will let some 60m readers of its service begin charging each other for the rights to access just about anything uploaded to the service.