Let's talk books!
This is where you include your bio, links to your online platform, previews for future books, etc. If you are with a traditional publisher, you will probably be limited in how much this can be updated. They aren't going to go in to edit and reformat your ebook just to add a new line to your bio. If you need changes, you'll need to contact your editor and discuss with them what is possible. However, if you are self-published, you can change this whenever you want. Now, that doesn't mean you should. However, if you have a new book out that you want to promote, adding a sneak preview to the back of your ebook is a great way to keep your fans reading more of your work.
I also suggest pointing readers to a central location on your website that you can update with listings of your books and new releases. And don't forget about the link to your Author Central account. Since you can tailor an ebook just to Amazon, this is a great way to point existing Kindle users to the rest of your Kindle ready books.
Regardless of how you are published, it's a good idea to give your back matter a check every once in a while to make sure that all the links included are still live and see if you have any major changes that need to be included.