Online retailer Amazon.com said today that it’s selling more electronic books than printed versions. The company says it sells 105 e-books for every 100 physical copies it sells.

Next Tuesday rival Barnes & Noble will ratchet up the competition when it introduces a new generation Nook e-reader to compete with Amazon’s Kindle.

B&N chief executive William Lynch told the Wall Street Journal that despite a late start his company has captured 25% of the digital books market. It has also grabbed a good chunk of the market for electronic magazine subscriptions. “We’ve also sold more than 1.5 million magazine subscription orders and single copy sales on the Nook newsstand.”

The irony of Tuesday’s announcement (or maybe the marketing strategy) is that it happens during the week of BookExpo America (BEA), which bills itself as the largest publishing event in North America. It has traditionally promoted paper copies. This year BEA will co-host a session on electronic publications with the IDPF Digital Book Conference 2011, at the Javits Center in New York City.