My eAudiobook is racing along so fast the reader sounds like Alvin and the Chipmunks.
Before you start troubleshooting, make sure your eAudiobook is fully downloaded. If it isn't downloaded, it's just streaming and that can create a host of issues. eAudiobooks do take longer to download than eBooks.
If it is completely downloaded, start the book and look for the playback speed icon. The icon will look different depending on the type of device you have. For example, on an iPhone 6s, on the bottom left-hand of the screen you'll see 1X. Other devices, it may look like a mini-speedometer. You can tap on this icon repeatedly to speed up the narrator's voice. It will eventually go so fast and then start over slow then return to normal.