Can I create an audio book from a InDesign file

Alas, "Video books" are nothing new. Even before the internet books were regularly converted to VHS format videos with images from the books, voice overs reading the book aloud, text appearing while reading, and crude animations / pans / zooms added to visually spice up the video book.

When DVDs and CD-Roms became popular, the 'video book' format was extended to include some level of interactivity. DVDs could include branching from one scene to the next. CD-Roms obviously expanded a lot on this, and the first video-based games were created. And it was quite popular to convert books to the interactive CD-Rom format as well. I still have "Mouse" and an interactive Shakespeare video/read aloud CD-Rom stuffed in a box somewhere up in our attic. 🙂

ePub video books are also nothing new or original. Students of mine have created these in my classes: they use after effects to create video sequences, add voice overs, include text in either InDesign and/or in the After Effects rendered videos. I've created FXL video books myselves (but stopped doing so after 1 or 2 projects, see below).

And of course, web technology and apps are used to create interactive animated books with voice overs. Just google animated comic books.

As for your idea and the practical / technical execution - a hint of reality:

• only fixed layout epubs (EPUB3) support video.
• FXL EPUB3 files are only properly supported on the Apple platform. Windows and Linux users do NOT have a standard FXL epub reader installed. They MUST install a third-party reader.
• On Windows and Linux the only viable FXL epub reader is Thorium. https://www.edrlab.org/software/thorium-reader/
  (Adobe's own reader is an embarresment on many levels and will not properly display or execute InDesign's FXL epub files)
• Because InDesign uses proprietary non-compliant linking code in the exported FXL epub files, these links do not work in any other reader except the Apple reader. 
• Manual coding is required to fix page linking issues in the final published FXL epub files. But then they work fine in Thorium.
• GIF only support 256 colours, and 1bit transparency. It is also very inefficient in terms of compression. Avoid GIF if a video file suffices. 
• Video files in an epub file cannot be controlled much. They may auto-play, or not. It depends on the reader. Students and myself have encountered various issues regarding autoplaying videos in an FXL epub file. Some students combined multiple videos on the same page, and synching them up is impossible, aside from "click this video to play, then click the next one to play". Even the controls may show or not. Another thing that I found had to be fixed in code after export.
• It is not possible to introduce actions to move to a different time index in a video. Flash could do this, and it was quite powerful. InDesign and FXL epub files do not support this.
• In some cases InDesign might export non-compliant epub code. These pages throw and error in Thorium, and have to be manually fixed, or the InDesign page restructured.
• FXL interactive epub files do not work on Android. Period. 
• Synchronizing a video with a separate audio file is not possible in InDesign. You will need to combine them in After Effects or Premiere.
• InDesign's interactive epub features haven't seen an update in a decade since they were first introduced. It shows. In my opinion the rendered code needs a rethink, and is too Apple reader oriented (which was the only option at the time and much touted by Apple).
• Forget the Amazon Kindle market. These type of interactive FXL epub books do not work on their platform. Nor do they work on Kobos, etc.

In short: FXL epub files have proven themselves to be very, very fragile in both production and publishing. Not many users are willing to install a third-party epub reader just to read your video books. Apple users can just view them, but both Windows and Linux users cannot. In practice this means it is too much to ask from the average Windows user to install an extra reader.

And why should they? Most content runs off the web nowadays. Convenient, just works in a browser. Browsers support a wide range of interactive features - while the FXL epub 3 standard is still lagging behind and not even an official standard. Even Adobe seems to have left FXL epub 3 behind in favour of their own online publishing platform.

Which is why it is a good idea to consider the browser as your target platform or create an app that can be published on the app markets. You have two options:

1. Use Adobe's publishing platform. Advantage: it just works. Publish your book, and it works. Disadvantages: almost impossible to monetize. Completely dependent on Adobe's servers. It is impossible to export your book to a version that can be hosted on your own servers (and thereby monetize them). 
2. Get the In5 plugin, and export to the web with additional improved interactive features. And/or export directly to an app that works on Android and iOS devices. 
   You gain full control over your exported work. 
3. Another option is external software such as PubCoder, which converts InDesign files, and then enables export to the web and as an app. Much less expensive, but the interactivity and video content must be created in PubCoder - so perhaps less convenient depending on the workflow.
4. Or just completely forego InDesign, and instead build your interactive video book in a game development app such as Godot, Unity, or Unreal. So much more possibilities (In5/pubcoder pale in comparison), and full control over videos. Export to just about any platform, including web, apps, Windows and Mac executables, consoles, and so on. (This is what I do now - I am done with interactive epub files, unless a client forces me to go down that path.)

In short: video books are nothing new under the sun. And I would avoid FLX epub files altogether at this point: target the browser or create an app instead. FXL epub files prove to be too fragile. In particular when dealing with slightly more advanced video.

Just my two cents.