how to remove a book from iBook

If you are asking about a book that you've bought from the store then you can hide it from the cloud so that it doesn't show for redownloading (you can't delete purchases) : Hide and unhide purchases in iTunes or iBooks on your Mac or PC - Apple Support

Thank you King_Penguin for including the link. I have searched several threads and while many gave some instructions, I wasn't able to follow them. This link was exactly what I needed. All the best!