Sales in Amazon’s North America media group, which includes book sales, rose 21.7% to $1.20 billion. Total company sales increased 37.1%, to $4.13 billion and net income increased from $111 million to $143 million. The e-tailer had little to say about the sales performance of books, though it noting that the number of e-book titles compatible with the Kindle is now at 115,000 compared to 90,000 at its November launch. Chairman Jeff Bezos said after working hard to increase manufacturing capacity the Kindle is now in stock. The company has had a difficult time keeping up with demand since the e-reader was introduced.

CFO Tom Szkutak wouldn’t comment directly about the decision by New York State to collect sales tax from out-of-state online retailers, but noted that Amazon already collects sales or value added tax on about 50% of its business.

In a revised prediction for the year, Amazon said it expects sales to increase between 29% to 35%, up from 26% to 33%; operating income was changed to a growth rate between 13% and 40% from 20% and 40%. The company said uncertainty in the global economy and currency fluctuations make it difficult to more precisely predict results, although Szkutak suggested that the softening economy didn’t have much impact on first quarter results.