Since consumer electronics retailer Circuit City Stores Inc. closed its doors and sold its assets to Systemax Inc., Best Buy Co. and Wal-Mart Stores Inc. have taken about two-thirds of their former rival’s market share, according to a new NPD Group report, New Look at Retail: Post-Circuit City.

While most of Wal-Mart’s gains came from its bricks-and-mortar business, Wal-Mart is No. 13 in the Internet Retailer Top 500 Guide.

From March to December 2009, Best Buy’s combined online and offline share of the notebook computer and digital camera markets gained 5.5%, flat-panel televisions increased 5.2%, and desktop computers gained 4.7%. Wal-Mart posted a 3.2% gain in flat-panel televisions, a 2.7% increase in digital cameras, a 2.3% gain in notebook computers and a 0.3% gain in desktop computers.

Despite the growth, it may be a tough fight for both of them to score further gains, says Baker. It was easy to pick up Circuit City’s market share, but there isn’t as much easy share to pick up anymore.

Best Buy appears to be looking for growth in the burgeoning market for electronic book readers. The consumer electronics retailer announced yesterday an exclusive agreement with Barnes & Noble Inc. to carry the bookseller’s Nook e-reader, beginning April 18. The agreement makes Best Buy the first retailer to sell the device outside of Barnes & Noble.