Book application no longer showing how many pages are left in the chapter

Hi AuntBite23,

Thanks for contacting Apple Support Communities!

We understand that you'd like to revert your Books app to a previous version.

The iPadOS doesn't include a feature which would allow you to install a previous version of a built-in app once the iOS has been updated.

The article you came to us from will show you how to use the Books app in iPadOS 16: Read books in the Books app on iPad - Apple Support

"Read a book

Tap  or turn iPad to landscape view to automatically view the sidebar, then tap a category such as Reading Now or Want to Read. Tap a book cover, then do any of the following:

• Turn the page: Tap the right margin or swipe right to left.
• Go back to the previous page: Tap the left margin or swipe left to right.
• Go back to where you started reading: Tap the page, then tap the rounded arrow in the top-left corner of the page. Tap the rounded arrow again, but in the top-right corner, to go back to your current location.
• Go to a specific page or location: Tap the page, tap , tap Search Book, enter a word, phrase, or page number, then tap a result.
• Use the table of contents: Tap the page, tap , then tap Contents.
• Tip: To quickly move through a book, touch and hold Contents, then drag your finger left or right; release your finger to go directly to that location in the book.
• Close a book: Tap the page, then tap  in the top-right corner, or swipe down from the top of the page."

We hope this helps you.

Take care!