I'd definitely buy it.
Not sure if it's in line with your interests, but for my personal interests, it'd be great if there were both technical content and some sort of coverage of the more conceptual/media issues involved in emulation (which overlap with the technical content). Stuff like fidelity of translation, stuff that's harder/easier to emulate, different layers of hardware, etc. E.g., some console emulators have recently added CRT emulation, because of a feeling that playing games designed for a CRT, especially 1980s CRTs, on an emulator running on an LCD gives an inauthentic effect (the CRTs do a bit of blurring in both the spatial and time domains). Or, how easy/hard is it to emulate something like the Atari's audio chip or the SID? Apart from the display and audio output, are there other things that don't translate well, or are hard to do well? It seems it's often the case that console emulators will choke on a minority of games, which must be doing something weird that isn't quite properly emulated; how common is that, and do they fall into certain kinds of categories?
Again, not sure that's actually in your scope, because it's not at all relevant for some kinds of emulation, e.g. pure CPU emulation, but has more to do specifically with audiovisual media. But I do want such a book. ;-)