Deleting Mom’s iBooks

My mother loved to read. I got her an iPad early on and she learned how to use it not only to send emails, but to look at photos, and read. She had macular degeneration so having the ability to make the print larger was so helpful. So she learned how to purchase and download books. Mom passed away two years ago and all of her books are still on the account because I set it up using my information. My husband has a replacement ipad that we received after I sent my mom’s in to get repaired. They couldn’t fix it so we got this one instead. It doesn’t have a lot of memory or space. So lately he’s been getting notices that he has run out of room. He too likes to read on his ipad. Also a month ago we turned on the iCloud photo option on our devices - something I didn’t want to do but had to because photo stream stopped working. There are thousands of photos now on all of these devices. So I’ve been spending time to delete whatever we don’t need. Aside from that we removed several apps from his device that he never used and freed up space by removing some of his subscriptions. It was kind of sad when I finally deleted my mom’s email account and I had the same feeling when I tried to remove the books - but I couldn’t. They just wouldn’t disappear. I have a feeling I will be forced to contact Apple support but just don’t feel like it. Let’s hope the space issue disappears. But I have my doubts.