As I sit here with half my arm swollen up from a sting I got yesterday (a "large local" reaction), I have come across the very-best-ever information resource on bee stings. It's written by a physician who is also a beekeeper (Buddy Marterre, MD), and it gives a great overview of the whole immune response. It explains the immunology, allergy, and treatment of stings at a technical level, but it is definitely accessible reading for non-scientists. It is also well-illustrated with photos and charts, and has a good set of reputable footnoted sources. It is a 4.8 MB pdf file, in two parts, downloadable from this link:

I discovered that this article has been referenced before in BeeSource, most recently by Luterra in this thread:
but I wanted to give it its own thread so that it would be easy to find.