I tried to turn off dark mode and it didn’t work

I tried all the ways to turn off dark mode so I could read a book with a light background instead of that hideous reverse video dark background. Nothing worked. Tried settings, light mode, removed all the auto settings. Checked that inverse thing, not on. Tried hold down brightness from top swipe, dark mode showed off. But not off on books app! It should have worked based on all the how to posts, but no! I turned off the iPad, waited, turned it on again, and Apple Books is STILL auto enabling dark mode. I hate dark mode! I just want to read a book at night the way I want to read it! Help! Can I restore to a previous iOS version? BUGS! Please fix the Apple Books app to RECOGNIZE DARK MODE IS OFF!