Borders Group ( BGP ) launched an electronic bookstore Wednesday, entering a market dominated by Amazon ( AMZN ), Apple ( AAPL ) and Barnes & Noble ( BKS ). But the No. 2 U.S. bookstore chain by sales is optimistic about its chances, believing it will quickly catch up with rivals and win a piece of the fast-growing e-books sector, Reuters reports. Along with its e-bookstore, Barnes & Noble launched the Nook e-reader nine months ago. Amazon sells the popular Kindle e-reader and Apple markets the iPhone and iPad, which debuted three months ago. Borders is clearly behind -- at least for now. With sales at its bookstores and website down over 11% in the first quarter, Borders needs a piece of the growing e-book segment. Some analysts believe this category could grow from 3% of total book sales in the U.S. to nearly 13% by 2015. An Uphill Battle Armed with data on 38 million customers, Borders believes it will easily capture market share. Borders' goal is to secure a 17% share of the e-book market by July 2011.