You can use your voice to ask Alexa to begin reading by simply saying "Alexa, read book title." Or you can navigate in the Alexa companion app under the new Kindle Books section to see which of your titles she can read to you. Out of the 200+ Kindle books I own, only a handful of titles aren't supported by the new service.
Amazon previously purchased Audible's audio book service, so when I saw the news in an Amazon newsletter, I figured there would be some fee to have Alexa read content aloud.
Nope, there's no charge. You'll have to be willing to hear Alexa's semi-robotic voice for reading instead of hearing professional talent read to you - which is typically what Audible uses - but after just a few minutes of listening to Alexa, I don't mind.
Alexa uses Amazon's Whispersync technology so she'll pick up right where you left off in a book. Unlike Amazon's Audible service, however, in-book navigation is a bit limited. In Audible, you can specify which chapter to read or move to.
Not so with Alexa: You can only tell her to skip back or pause, although in the Alexa app, you can easily tap a button for 30 second skips in either direction or move to any chapter you want.
I can live with that because the read aloud function is yet another useful feature Amazon has added to the Echo, which is a device I use multiple times each day already for music, controlling lights and asking for information.