Here is a simple little Python script that uses BeautifulSoup and requests to download all the books from the purchased books page.
http://paste.openstack.org/show/625665/
You of course need to have purchased the books to access that page :)
Using Firefox, I do: File->Save Page As
Then save it. Rename the *.html file to index.html and then run the script.
http://paste.openstack.org/show/625665/
I did this because I was too lazy to click Save As 30+ times :)