The Save button is disabled when I try to update reading progress. Why?

This usually happens if the book has a reading status created with 0 pages. In that case, the app doesn’t know how to calculate progress.

To fix it:

1. Open the book.
2. Long press the current reading status and choose Delete.
3. Tap Add Reading Status and enter the correct number of pages.
4. Save again, the Save button will now work.