Hi
The "Published Guides" for OpenOffice or LibreOffice are often the best
documentation for AOO or LO - at least for English readers. The LO ones,
including incomplete books and archived versions, can be found at;
https://wiki.documentfoundation.org/Documentation/Publications
for free or bought from the Lulu bookstore as proper paper-back books. I
bought a few of these and I'm really glad i did even though i haven't read
all of it yet! I think i managed to time it right so that Lulu were
offering one of their frequent discount weekends or something.
The guides are also available in various App Stores or online book-stores
for reading on-screen; such as the Apple store, the Ubuntu one and maybe
others. They usually cost a bit but not much. Enough to cover the costs
of publishing them in those places and a little more to allow a bit of
expansion in their distribution.
Also available on the official LibreOffice website (for free of course!);
http://www.libreoffice.org/get-help/documentation/
For non-English languages it is usually the 'in-built' help that is far
better.
There are also on-line videos such as the excellent range at Spoken
Tutorials;
http://spoken-tutorial.org/
although they cover a much wider range of OpenSource projects so you'd have
to hunt for LibreOffice in that lot Also while English is excellent
they also do many languages from around the Indian basin as it's a
non-profit organisation largely funded by the Indian Government.
Regards from
Tom