Amazon.com posted a 45 percent decline in quarterly profits this afternoon, but Jeff Bezos says one of the company’s biggest benefits is paying off, as digital books and the company’s Kindle business show significantly greater momentum than traditional books.

“We’re now seeing the transition we’ve been expecting,” said Bezos in the company’s earnings news release. “After 5 years, eBooks is a multi-billion dollar category for us and growing fast – up approximately 70% last year. In contrast, our physical book sales experienced the lowest December growth rate in our 17 years as a book seller, up just 5%. We’re excited and very grateful to our customers for their response to Kindle and our ever expanding ecosystem and selection.”

Amazon doesn’t disclose Kindle unit sales numbers, but the company noted that Kindle Fire HD, Kindle Fire, Kindle Paperwhite and the Kindle held the top four spots on Amazon’s overall bestseller list since they were launched.

One of the company’s biggest rivals, Barnes & Noble, reported a decline in sales of its Nook device for the holiday quarter.

Previously: Kindle Fire scorching Android tablet market with 33% share

Like what you're reading? Subscribe to GeekWire's free newsletters to catch every headline

Job Listings on GeekWork

Find more jobs on GeekWork. Employers, post a job here.