Have you created a vocabulary for these books?

If not:

1. Create vocabulary, e.g. "books_category"
2. Add to your content type field e.g. "books_category"  (field type: Term reference) as a reference choose your new created vacabulary "books_category"

After you do that, click at replacement paterns ( admin/config/search/path/patterns  ) Choose group "Tokens related to individual content items, or "nodes" There you will find a group of paterns related to your field "books_category"

• I assume that you have installed Pathauto module

Have you created a vocabulary for these books?

If not:

1. Create a vocabulary, e.g. "books_category"
2. Add to your content type field, e.g. "books_category" (field type: Term reference), choosing the vocabulary you previously created as reference

After that, click at replacement patterns (admin/config/search/path/patterns); choose group "Tokens related to individual content items," or "nodes"; you will find a group of patterns related to your "books_category" field.

I assume you installed the Pathauto module.