Recommended for experienced practitioners. Thatcher gives clear step by step descriptions of how we actually/literally/physically perceive things. It is not necessary (nor possible) to access these states of mind all the time but knowing they exist ..."give(s) a student more confidence in the method of insight meditation." Too often we are given dramatic or poetic descriptions of the process which can end up making it seem more esoteric or "out there" than it actually is. This look at the mechanics of how things work is a much more accessible version than is offered in other books on the same subject.
Wonderful introductory books for beginners by Salzberg, well-known Vipassana teacher.