OK, I'm interested. Can you explain a little more?

What are your motives for learning about it? If it's to gain a bare-bones understanding sufficient for following discussion in Less Wrong, existing Less Wrong articles would probably equip you well enough.

If you have the time, I heartily recommend Ben Polak's Introduction to Game Theory lectures. They are highly watchable and give a very solid introduction to the topic.

In terms of books, The Strategy of Conflict is the classic popular work, and it's good, but it's very much a product of its time. I imagine there are more accessible books out there. Yvain recommends The Art of Strategy, which I haven't read.

I want to know more (ie anything) about game theory. What should I read?

Vague stylistic thought - I don't have anything specific to base this on, but this chapter feels like something EY has been saving up, and is now throwing in as he's decided it's time to start the ending.

I noticed a strategy that many people seem to use; for lack of a better name, I will call it "updating the applause lights". This is how it works:

You have something that you like and it is part of your identity. Let's say that you are a Green. You are proud that Greens are everything good, noble, and true; unlike those stupid evil Blues.

Gradually you discover that the sky is blue. First you deny it, but at some moment you can't resist the overwhelming evidence. But at that moment of history, there are many Green beliefs, and the belief that the sky is green is only one of them, although historically the central one. So you downplay it and say: "All Green beliefs are true, but some of them are meant metaphorically, not literally, such as the belief that the sky is green. This means that we are right, and the Blues are wrong; just as we always said."

Someone asks: "But didn't Greens say the sky is green? Because that seems false to me." And you say: "No, that's a strawman! You obviously don't understand Greens, you are full of prejudice. You should be ashamed of yourself." The someone gives an example of a Green that literally believed the sky is green. You say: "Okay, but this person is not a real Green. It's a very extreme person." Or if you can't deny it, you say: "Yes, even withing the Green movement, some people may be confused and misunderstand our beliefs, also our beliefs have evolved during time, but trust me that being Green is not about believing that the sky is literally green." And in some sense, you are right. (And the Blues are wrong. As it has always been.)

To be specific, I have several examples in my mind; religion is just one of them; probably any political or philosophical opinion that had to be updated significantly and needs to deny its original version.

"So you also don't think it's worth the trouble of holding me responsible..."

This could be interesting depending how she reacts later. I'm mostly expecting despair, but with a small chance of a heroic Minerva.

Unlikely theory:

It's all a fake. Harry set the whole thing up with Dumbledore, then obliviated himself. The real Hermione has been spirited away somewhere she won't be in any danger. Harry relied on his own likely reaction to ensure things would occur more or less as planned.

We can keep Hermione alive yay! But it doesn't work dramatically.

Other unlikely theory:

Harry will calm down tomorrow and realise his vow was a mistake.

I kind of like this as what a saner person might do, but again it seems very unlikely within the confines of Harry and the story.

Notice though that Sophie's World only goes into philosophy up to Freud. The philosophy that Starts with Russell and ends with Drescher doesn't get any say on it.

It is a very fun book about very bad philosophy. But so is "A History of Western Philosophy" by Russell himself.

For general philosophical background I'd recommend Sophie's World. It's mostly history-of-philosophy, but I think it works well as a fairly light way into the field.