Amazon.com Inc. has acquired text-to-speech technology company Ivona Software for an undisclosed amount as the Internet heavyweight continues to step up its push to dominate the e-reader market.

Amazon's Kindle Fire tablets already use Ivona's technology to power their "Text-to-Speech," "Voice Guide" and "Explore by Touch" features. Ivona also delivers text-to-speech products and services for thousands of developers, businesses and customers around the world, Amazon said. The company currently...