Here is a set of essays on the calculus of nuclear war, written by someone who used to plan nuclear war. They are short, funny in places, reassuring in places, and generally scary.
Of course, no mention of nuclear weapons is complete without directing readers to the Nuclear Weapons Archive, by Carey Sublette. I remember first reading the FAQ in 1996 or so, and being astounded. It changed the way I thought about The Bomb.
It's the physics bit that got me. I had previously though of fusion bombs as being somewhat like the Sun, only, here. But it turns out that fusion in the Sun proceeds along quite slowly, at comparatively low temperatures and pressures. Fusion bombs operate at much higher pressures and temperatures than stars do, and (obviously) on much shorter timescales. It turns out to be almost completely different physics.
For some reason that really bothers me. The notion that we use physics that can't even be observed anywhere in the natural world seems odd. Perhaps I'm succumbing to nuclear hocus pocus, since I can't think of anywhere in the natural world that we can observe hydrocarbon-oxygen combustion at dozens of atmospheres of pressure, and yet our cars and airplanes do that all the time.