Online retail book sales will nearly double over the next five years, according to "U.S. eCommerce Overview: 2003 to 2008," a report recently released by Cambridge, Massachusetts-based Forrester Research. Overall, the study predicted, e-commerce will experience a 19 percent compound annual growth rate (CAGR) over the next five years, from $95.7 billion to just under $230 billion and will account for 10 percent of total U.S. retail sales by 2008.