Public Domain and Creative Commons-licensed books can be found in the SimplyE Collection or from Open Bookshelf. Tap the library icon in the upper left corner to toggle the catalog to either collection.
Free to keep books will display only a Download button in the catalog view. There is no hold queue and no expiration date on these items, and no login required. Tap the Download button to get the book. The button will change to Delete or Read once the book is downloaded. The book will also show up in the list under the My Books tab with a Read and a Delete button.
Note: Your Bookshelf in either collection will not sync between devices you own since you are not creating an account. This content in many cases can be accessed from your library's account, and can be easily downloaded and synced between devices there.