Your Adobe Digital Editions (ADE)  bookshelf display the items you currently have downloaded.

Each ebook will display the number of days remaining on the download period.

Once the download period is complete you will no longer be able to access the eboook

To return a book early, left click the mouse on the ebook image and select Return Borrowed Item from the drop-down menu.

To read an ebook, double right click on the cover image.  Use the Table of Contents icon to navigate the ebook.  Clicking on a chapter link will bring you to directly to that chapter.

Use the page icon to select the page size you prefer.