Jeffrey P. Bezos, Amazon’s chief, said sales of the Kindle 2 e-book reader had “exceeded our most optimistic expectations.”

Amazon.com has joined Apple among the ranks of technology firms that are still growing robustly despite a shrinking economy.

Amazon, the online retailer based in Seattle, posted stronger-than-expected earnings during the slow winter months, attracting cost-conscious consumers with offers of free shipping and competitive prices for its wide variety of products.

Amazon’s net profit rose 24 percent, to $177 million, or 41 cents a share, in the quarter ending March 31, up from $143 million, or 34 cents a share, in the same quarter a year earlier.

The company’s first-quarter revenue climbed 18 percent, to $4.89 billion, slightly surpassing Wall Street’s expectations. Analysts polled by Thomson Reuters on average had expected $4.76 billion in revenue.