This is a true gold-mine of information on origins of mathematical notations. Whenever I want to innovate in notations, I want to know how and why the traditional notation was chosen. This book tells me that. Then I can think about whether my new notation fits its purpose better than the old one.In my opinion, the importance of notations is very much underestimated. Anyone who has spent a lot of time reading old mathematics literature, going back hundreds of years or more, knows that the principal difficulty with reading old texts is the lack of good notation to express the ideas. Even books written 50 years ago are often painfully difficult to read because of their ill-chosen notations. Some subjects have surged forward when notations have improved, while others have languished due to the difficulty of expressing ideas in poor notations. When you upgrade old notations to new requirements, I think it's important to understand their history first.Another way to think of the importance of notations is that they give meaning to symbols in the same way definitions give meaning to words and phrases. But definitions serve to highlight the concepts which are most important in a mathematical topic. We define concepts because they are of enduring importance. And notations likewise highlight the most important concepts. But since a mathematical formula is a kind of picture, it is interpreted more by pictorial perception than linguistic perception. In other words, formulas are more like diagrams than text. We take (or should take) a great interest in the history of concepts. So we should also take a great interest in the history of notations!The only drawback of this book is the page numbering because it is "two volumes in one". The index for volume I is on pages 433-451 of Volume 1, in the middle of the book! So you really have to keep a permanent book-mark there for index look-up. Many times I have looked up things in the Volume 2 index at the back of the book, forgetting about the separate Volume 1 index.As far as I know, this is the only encyclopedic history of mathematical notations. Many books do give a few snippets of history about notations here and there. But this book is quite comprehensive and authoritative, up until the early 20th century anyway.