Many of the "lost states" fall into one of several types: territories which the U.S. either controls now or controlled at one time, separatist movements within existing states, different plans for boundaries of existing states (basically different ways to slice up territories), or far-fetched schemes to annex all or parts of other countries (there are entries here for Albania, Great Britain, Guyana, and Taiwan, for example).
While I'm not sure I would have included a few of these, Trinklein makes a good case for each, and I really liked the maps he designed for them (also, the dust jacket unfolds into a poster-sized map, if you're into that sort of thing). The tone is light, and that's perfectly okay.
Quirky, and great fun.
