
some books have roman numerals on their spines to denote
volumes

some books have their chapters numbered with roman numerals.

some plays have their scenes & acts numbered with roman
numerals e.g. Macbeth  Act iii, Scene iv

fantasy genre books like to use roman numerals

many books have information in the front and these pages
are often marked with lower case roman numerals e.g. i,
ii, iii, iv, x
NB
The 'forward' to a book is mostly written after the book
is complete so it easier to use a different numbering system
for the forward instead of renumbering all the pages in
the book.
Some
people believe that authors use roman numerals in their
books as they wish for the book to appear important. Other
authors may want to create a 'classical' mood and still
others wish to create an 'other worldliness'.
Task
 Find some books in your library that use roman numerals
and decide why you think the author chose to use this numbering
system.
NB
It is very rare that modern writers use roman numerals to
number chapters.