I've just started watching this show. I don't know why I haven't started before. I guess because I'm not really that interested at all in politics? Anyway, I'm still in the first season so I don't think these are going to be terrible spoilers, but I was a little surprised at how realistic the depiction of a high functioning sociopath seems to be for Frank Underwood.
There are the obvious things: obsessed with power, crafty, manipulative, duplicitive (spell check tells me that's not an actual word), has few intimates and the rest of his acquaintances are just pawns in his chess game. But there are also some of the less obvious things: bisexual, oddly friendly and helpful without any seeming motive and just as oddly vindictive in a way that seems to far exceed the original offense. He often does things that are generous with little hope of the good deed being reciprocated in kind, but he feels like "generosity is its own form of power". He's not delusional, but he also has random beliefs that don't seem entirely rational either, like a faith/belief in karma. If he respects you, he's not going to bullshit you, which may be nice for the open marriage he has with his wife (the marriage and love angle also seems like a pretty realistic depiction of the sort of partnership built on respect and admiration rather than love that you would expect), but he also clearly has impulse and rage problems and his crazy risks don't always pan out well for him. He's the type of person that you would love to have for a friend if you needed any of his prodigious skills, but also would need to watch yourself around, which maybe isn't that bad of a trade off?
Any way, I hope the subsequent seasons stay true to this character and for those of you who haven't seen this show yet, I would recommend it. Netflix.