The e-books linked below have limits on how many people can use them at one time. You might click on the book link and find you cannot open the book. This just means you have to wait for some period of time until it is available. These books can not be checked out.
Once you get access to the book, you are permitted to download a set number of pages. Use the orientations in this guide to find out how to do this. Note that the download limits will reset if you log out of your "session", in other words, close the book. You will be able to download another set number of pages.