I question its value as a teaching tool, though. I fear the Victorian niceties employed in the exposition will seem stilted and nigh unbearable to today's younger audience, especially if assigned as schoolwork. But, I think those who already grasp the mathematics involved (basic geometry) will enjoy it. Also, A. Square's unabashed enthusiasm and thirst for knowledge are qualities one would happily encourage in students.
My favorite part of the whole book has got to be the visit to the King of Pointland. The way Abbot so succinctly portrays humanity's capacity to ignore evidence that does not conform to preconceived notions, then force the facts to fit long established beliefs is a stroke of genius. In Pointland, ignorance really is bliss.
This little tale definitely provided excellent entertainment for the price I paid here at Amazon. If it sounds interesting to you, I suggest putting it on your wish list, and then adding it to the next purchase you make (your wallet will barely feel it).
An examination of Theosophical Society literature from this period will also show a fascination with the 4th dimension as an explanation for spirit phenomena. Personally, I believe that this train of thought is still a quite valid analogy.
I found this book a joy to read, but then, I was trained in classical Euclidian geometry and formal proofs as a boy. I understand that such training is quite extinct in most modern public schools....