Hello Andrea
The Help page you visited is incomplete and has a bug after it has been
converted from the local help.
You can download the local help here
http://download.documentfoundation.org/libreoffice/stable/5.3.0/win/x86_64/LibreOffice_5.3.0_Win_x64_helppack_en-US.msi
You'll find more
Progress report on the revised published GS 5.2 files
Here are the errors I have found and corrected in the *book* file:
1) Tools > Outline Numbering had the wrong heading levels defined, so
when the TOC was updated, it lost all the chapter names ("Title"
paragraph style).
2) Footer on copyright
