You are limited only by your imagination in qualitative justification. However, work with your department head to make sure that your primary evaluator agrees with your methods of evaluation.
Book chapters and full books indexed by Web of Science's Book Citation Index (BCI) include the number of times that book has been cited. Note that only citations within books and articles indexed in Web of Science are counted so the actual citation count is likely to be higher than that given in this database. Citations can be counted in other Web of Science databases as well.
This image shows that the sample work was cited 10 times in Web of Science Core Collection. Below that, the option to show more was chosen and this work was cited 5 times in BIOSIS Citation Index and 0 times in all the other Web of Science non-core databases.
This reference book describes the top journals and magazines in many different subject areas. Use the reviews as evidence of the importance of a particular journal or magazine. Reviews may also be found online through the Ulrich's database. Search Ulrichs for your journal title, then select the "Reviews" section of the journal entry.
Book reviews are excellent sources of evidence of the quality of your book or book chapter. These generally appear anywhere from the time of publication to about a year after publication depending on the publisher. Using excerpts from reviews can be found by searching the primary databases for your field and using the word review. Some databases have a publication type of review that can also be used to narrow your search down to reviews. You can also search the Library and Information Sciences and Technology Abstracts database for reviews. This database indexes Choice and Booklist which are publications of reviews that librarians use to help determine what to buy. The reviews in these sources are typically short and evaluative.
Reputations of editors and publishers can be used as evidence of the quality of your work for books; however these reputations must be explained so those outside your field will understand the reputation and how that reputation reflects your work.
You can use reviews of other works with the same editor as your work if that review discusses the reputation of the editor. Their reputation may also be evidenced in biographical works. Don't make the review committee take your word that the editor is prestigious if you want to use that person's reputation as evidence of the quality of your work, but give the committee some outside evidence of the editor's influence.
Publisher reputation can be a difficult thing to document. Book reviews of books published by the publisher can sometimes include statements about the publisher and these statements can be used. Also, professional associations will sometimes list the "best" publishers for their profession and that can be used as documentation as well. Academic presses speak for themselves to a certain extent but you will want to make sure that you document the review process that your manuscript went through.