First of all: A Beauty Cold and Austere is extremely well coded and implemented. Every action I tried that had even the slightest relevance to the problem at hand was understood. The parser understands tons of synonyms and guesses accurately what you want to do from differently formulated commands. This is a joy in every adventure, but it is doubly so in a game like this. There is a lot of precise fiddling of switches and turning of dials here, and any less near-perfect implementation would have made this a hell of frustration.
The puzzles here are logic and fair (duh). The author has put in a lot of effort to guide the player to understanding why the solutions work. I daresay that I have learned a (vague) thing or two about calculus.
The game truly shines in its visualization of abstract mathematical concepts and problems. An algebra problem made concrete with balancing scales is something one could find in an oldschool text adventure. Making an infinite converging series tangible or visible is harder. And programming, nay, creating a working machine in the game that lets you manipulate such series at will is just a heavenly present to any IF-tinkerer.
The writing is very good. Well-described locations, the occasional joke (well, a bit more than occasional, but it stays within bounds...), good NPCs. On the larger scale, it's harder to say:
Like The Chinese Room, a game that explores some basic concepts of philosophy, A Beauty Cold and Austere explores many mathematical concepts. And, like The Chinese Room, A Beauty Cold and Austere does not have much of a story beyond that.
It makes up for this though. Instead of a story-structure, we get an ever-widening understanding of mathematical concepts and how they are linked to eachother. And this widening understanding is beautifully reflected in the way the gamespace evolves. The map itself expands and deepens with your mathematical discoveries (or inventions, depending on your philosophical standpoint). You also have the backbone of math's history and many of the great minds in it to give the game a recognizable structure.
I like this game a lot.