Evaluate some data for addressables

Tell me pls, is there any best practice to evaluate some sort of data for addressables? For example, I'm creating something like interactive book, so pages are asset references, and each page contains list of asset references. And I need to find how many objects of certain type or any type in all book before load pages and objects.

For now I made serializable variables in root script (let's call it book), and when someone adds asset reference to page, page script fires an action from OnValidate method. Book catches this event and re-calculates all of this variables. But this approach looks messy to me.