Amazon Inc. announced a thinner, lighter entry-level Kindle e-reader on Wednesday. Yet the biggest new feature turns out to be the return of accessibility for blind readers.

In earlier days, Kindles had speakers, headphone jacks and text-to-speech functionality that could help readers who have trouble seeing text. But the fourth-generation Kindle Touch, which came out in 2011, was the last of these. As Amazon ramped up its LCD-screen Fire tablets, it removed audio features from the Kindle e-reader line, making it inaccessible...