Only if you have stored files locally and select “also delete local data” when deleting the app. You can check this in the Files app or by connecting the device to a computer and browsing the books storage section.

Anything backed by icloud storage (and of course anything purchased from the store) can be redownloaded later.

As a compromise, you can “offload” the app until you’re ready to use it again from the apps section of settings. This has the side effect of retaining existing data while uninstalling the app itself.

Are you asking if you delete the Apple Books app from your iPhone if it will delete audiobooks purchased from Apple from your phone, I’m pretty sure the answer is yes. I don’t think these purchases show up in any other app.

If you delete them, you should be able to redownload them from the Books app/store without repurchasing. However, I would still make a backup of your purchases on a computer because record companies and other publishers have a nasty habit of pulling items out of circulation because of licensing disputes and whatnot. Better to have a local backup just in case.

https://support.apple.com/guide/books/download-purchased-and-updated-items-ibks888f2d84/mac

https://support.apple.com/guide/itunes/download-previous-purchases-itns36a8f323/windows