The Document Foundation maintains a library of user manuals for the elements of the LibreOffice suite. The 4.0 branch of manuals have been getting published since its release and several have appeared just recently. If you find a lot of work involves using LibreOffice, these manuals will surely come in handy.
Last month, The Document Foundation released the 4.0 Writers Guide, which helps one in "word processing with style." In the last couple of days announcements for the Math Guide, Base Handbook, and Impress Guide were made.