Now click on Tools, then Start Text-to-Speech (or press Ctrl-T on a PC, Cmnd-T on a Mac) to start reading the book from the top of the page. Once you have installed the app on a Mac or PC, and logged into your Kindle account, click on the book that you wish to read. The Mac and Windows versions of the App are very similar, but the screenshots in this blog are taken from the Windows version.
(In the case of the Apple app, you currently get version 1.12.4 from the App Store, but version 1.19.1 from Amazon. To get the latest, free version of the app, make sure you go to the link on the Amazon web site, not the Apple or Windows App Store as the App Store versions are quite old. All this has changed with the latest versions of the apps, available from Amazon, which can easily read out text from speech-enabled books using your computer's default voice. Text to speech has been available for some Kindle book readers for a number of years, but if you wanted to add this feature to the Kindle apps for a Windows or Mac computer, this involved an incredible amount of faffing about.