How do I update iTunes' selection of books from iBooks?

Question

I use iBooks v. 1.1 on a MacBook Air (13-inch, Mid 2012) running 10.10.1 with iTunes 12.0.1.26. I use iTunes with both an iPhone 5 and an iPad, both of which use up-to-date (Jan 15, 2015) iOS and iBooks apps.
I have a lot of books and PDFs in iBooks on the MacBook; they show up there. In iTunes, however, I only see a limited selection, which I think might be a selection I loaded onto my iPhone or iPad maybe a year ago. I've tried relaunching both apps, rebooting the computer, using the "Move from iTunes..." command in iBooks (on the MacBook, to no avail. I still see only a limited selection.
This *****. I can't get most of my PDFs and books to my iPad or iPhone, which is where I do my reading. I'm ready to switch to some other platform - maybe a paper-based one again. I like reading!

Answer 1

You can also see a list of all your iBooks purchases directly in the iBooks application itself without having to launch iTunes on your computer. In iBooks, go to your library (the bookshelf) and then click the "Store" button at the top right.  Next, click the "Purchases" tab at the bottom right.