A better example might be related to the Roman emperor Augustus. Memorizing the various events of his life, his personal quirks, and so forth is absolutely going to give you a sense of the man moreso than just reading a random biography about him.
I do agree that a book provides the "gist" of the subject's character, but I think you can get that from watching a 30-minute documentary, not reading a 500-page book.
> All this information is stored somewhere in your brain in some way.. it can possibly be used at some point without you even realizing.
It's a pretty big assumption, if you're implying that we somehow remember everything we read.
In any case, I think the best approach is probably to combine reading a book with specific facts that easily fit into a SRS system. This is something I've been thinking about quite a bit, in fact: how would one design a narrative-based book such that it is more easily remembered? My initial thought is something like this: at the end of every chapter, a list of 100+ specific points made is presented. You could also include a premade Anki deck with the ebook edition.