I’ve had my Kindle for years, and I’ve figured out a few tricks to manage my library books without always returning them. If you want to remove a borrowed book without officially returning it, you can do so by archiving it. Go to your Kindle’s home screen, find the book, press and hold the title, and select 'Remove from Device.' This won’t return the book to the library—it just removes it from your Kindle. The book will still be in your Amazon account under 'Manage Your Content and Devices,' so you can download it again later if you change your mind.
Another method is to turn off your Wi-Fi after downloading the book. As long as you stay offline, the book won’t automatically return when the loan period expires. Just remember that once you reconnect, the book might disappear if the loan has ended. This is a handy workaround if you need more time to finish reading. Also, if you use the Kindle app on your phone or tablet, you can remove the book there without affecting the library loan. It’s a bit of a gray area, but it works for me when I’m not ready to let go of a book just yet.