The PrestaShop community is thriving, and some of its members are happy to create their own documentation. While they are in no way official, we are happy to give them a link, as a thank you for their hard work.
If you created something PrestaShop-related, please let us know!
Please note that the only official PrestaShop website is at http://www.prestashop.com/.
There are also many language-centric sections on the official forum.
You can buy the official PrestaShop 1.5 User Guide on Lulu.com. You can also buy the official documentation in PDF format on Addons.