thesaurus.maths.org

A book is a piece of writing, occupying several pages; it may be the physical object (the collection of pages, bound at one edge between covers stiffer than the pages) or the text printed or written on these pages (usually at least long enough that it could be bound as a single volume, even though it may not be in practice).
There are a few famous books (in the second sense) in mathematics, for instance Euclid's Elements
and Newton's Principia Mathematica. Sometimes, as with Euclid, all of what we know about a mathematician is that he is said to have written a particular book.