Barnes & Noble Inc. (NYSE: BKS) surprised Wall Street today by reporting quarterly earnings that did not suck as bad analysts expected, mainly because it was able to control costs. The question is whether this is sustainable.

Net income at the world's largest bookseller fell to $15.4 million, or 27 cents a share, from $18.05 million, or 26 cents, a year earlier. Sales dropped 1.6% to $1.2 billion from a year earlier when J.K. Rowling's Harry Potter and the Deathly Hallows was flying off the shelves. Barnes & Noble store sales decreased 1.6% to $1.1 billion, with comparable store sales decreasing 4.7%. Barnes & Noble.com sales rose 3.6% to $99.8 million.

Excluding a one-time tax benefit, profit was 15 cents, five cents ahead of the 10-cent average estimate of analysts surveyed by Bloomberg. It was also higher than the company's guidance of 8 cents to 13 cents a share. Gross margins were stronger because of the greater utilization rates of its distribution centers and a lower markdown rate. Selling and administrative expenses fell in the quarter.

Of course, Barnes & Noble will continue to struggle as consumers cut back on their discretionary purchases. Moreover, Amazon.com Inc. (NASDAQ: AMZN) is not going anywhere soon. The company expects to lose 10 to 15 cents in the third quarter. It also lowered its full-year comparable same store sales guidance from "slightly negative to a decrease in the low single digits." The company is maintaining its full-year earnings guidance of $1.70 to $1.90.

At this rate, the company may be able to ride out the economic downturn until it can find a private equity buyer which is about the only hope for shareholders.