Deciphering Character

I just finished rereading Brandon Sanderson's novella, "The Emperor's Soul." This is a fantasy novel with a complex, original magic system. Recently, I have also read some of Sarah M Eden's books. She primarily writes clean regency romance. Today I realized that I actually like "The Emperor's Soul," and Eden's books for the same reason, or at least some of the same reasons.
"The Emperor's Soul," is about a girl who is a master forger, and in her world that doesn't just involve the typical type of forgery we have in out world but with an intricate type of magic if she knows the history of an object she can essentially rewrite it's presence. But what is cool, is that she does it for a person. In order to be successful she has to do a ton of research. She not only has to know what his favorite color is but why... even if he did not know himself. This is because:
 "a person [is] like a dense forest thicket, overgrown with a twisting mess of vines, weeds, shrubs, saplings, and flowers. No person [is] one single emotion; no person [has] only one desire. They [have] many, and usually those desires conflicted with one another like two rosebushes fighting for the same patch of ground." The whole book is about how she not only learns about the Emperor (who she is trying to forge) but also those around her as she discovers their motivations and their own deceptions and idiosyncrasies.
Eden's books are usually categorized as clean romance, which they definitely are, but unlike many romances (and just books in general) her characters are very well rounded and as the hero and heroine get to know each other they are discovering each other's motivations, and deceptions and idiosyncrasies, and why. Just like getting to know real people they are slowly piecing together each other through words and actions and sometimes they are able to come to conclusions that are true but might not even be recognized by the person. I just reread her book "Seeking Persephone" and Persephone recognized that Adam is shy, genuinely uncomfortable talking to people. Yet when you are in Adam's point of view he never once thinks of himself as shy.
I feel like I'm pretty self aware (I have made some of those types of connections about myself before) and I also find if fascinating to observe and talk about this kind of thing in other people. Plus, doing this well is one of the more rewarding parts of writing. So, I guess it is really no surprise that I like reading about it too.