Is my book the most highly cited in its field?
To answer this, you need data on how many citations there are to your book and to others in your field. There are two sources of citation data for books, that I know of:
- Thomson Reuters' book citation index. Not everyone will have access to this, of course, as it's a subscription product.
- Google Scholar: this is available to everyone and is the source I've investigated.
A simple search for your book on Google Scholar will tell you how many citations there are. Note that G Scholar does try to collate records for all versions of your book, but for books available in many editions and reprints, then it might not be too successful at this!
Next, how do you know if your book is the MOST highly cited in your field? It's impossible to tell really, but a good clue is to invstigate the "related articles" link in the results of your search that brought you data about your book. This will find items that are similar to yours so therefore are likely to be in your field.
Within that list, there will be citations and journal articles as well as books. You can look through the results and spot books quite easily: look at how many times the books have been cited. If any are more highly cited than yours, then you know that your book can't be the most highly cited in your field, at least as far as GScholar is concerned. Whether or not you choose to trust their data on citations is a separate matter!
If none of those citations are anywhere near your citation count, then it would seem that there is a good chance that your book is one of the most highly cited in your field. You probably know some of the competitor books to yours: try searching for them on Google Scholar too, to check.
If you don't already know competitor books in your field then I recommend looking on the COPAC union catalogue at the record for your book, and clicking on the subject heading links from within that record to find books in the same subject category.
Best of luck!