The option to export you book as a video is only available in Book Creator for iPad. This is because we believe publishing your book online is a far superior alternative, which allows readers to interact with your book and still available on multiple devices.
However, if you do want record your book, you could try screencasting your book. This is a technique we regularly use to share snippets of a book via social media, like the one below. You could start the recording, then click the Read to Me button and the book will read itself.
On Chromebooks, we use the Screencastify Chrome extension, which is really simple
to use and gives you the option to export as an MP4 file or a GIF.