How to create and group reports by topic in Google analytics?

Question

Google Analytics

There is a site, let's say about books. And you need to get reports on how much they are interested in what genre.
The problem is that you can't just take and track categories, since there are still separate posts and pages about the same genres. In addition, the same page can simultaneously fall into different headings (genres).

Actually, the questions are:
a) are there any special meta tags to which post tags (genres) can be passed so that they can then be used to create reports in GA?
b) how can you set up data grouping and glue the statistics of a category and just pages and posts that have a common tag "under the same roof" so that you can see the statistics for this particular set of pages?