When I download a book in Apple Books, It doesn’t stay downloaded on my iPhone

Why don’t when I download a book they stay downloaded? I have to use a second book app apparently.

also if I search for text in a larger book, the app will crash after loading a certain amount of results.

this page doesn’t allow for selecting a relevant topic.

Is this a problem for Apple devs that I use this platform, so they want to push me away? Did I do something to upset them?

[Re-Titled by Moderator]