Kathryn, it’s actually quite easy … you highlight a paragraph or two, and when the bubble menu pops up, you tap on “copy” and then go paste the text into where ever you want , an Apple Note, Pages, Word, any text site. If “copy” isn’t showing, then tap the arrow on the right and more options appear, including “copy.”
You can usually only copy 1-2 paragraphs at a time, but then you just highlight the next section of the text in Apple Books and paste. You can copy & paste as much as you want; I’ve never been limited on copying text.