Creative magic systems are a long-standing feature of fantasy. Sanderson has chosen to specialize in them. While I recently ran across a comment suggesting audience interest was thinning out, I disagree. In fact, I'm beginning to be a little in awe of Sanderson's output. Fantasy is often weaker on ideas than science fiction, but makes up ground with character and story. Sanderson's strength is that he's able to bring ideas and character together - and the speed with which he keeps creating interesting, logically consistent worlds populated with likeable characters is astounding, especially because they're good.
The Rithmatist is more of what Sanderson does well - young folks discovering more about their world and its magic. He's taken some liberty with steampunk, and the tone of the bookis very much YA, as are the characterizations, but the former is no flaw, and the latter is not a major impediment to enjoyment. It's true that I sometimes felt the story being constructed around me (sort of "let's have one of these, and drop a clue about that"), but it didn't get in my way.
The ending is very much a cliffhanger, and I'm a bit surprised it was issued as a standalone piece. Perhaps Sanderson felt another book on the Stormlight Archive scale would be too much. I was also surprised to find no references to Edwin Abbott's Flatland - a source seemingly tailor made for the concept. On the other hand, this is a book that really gains from the excellent illustrations by Ben McSweeney.
All in all, highly recommended. With the exception of the very weak Alcatraz, Sanderson is proving one of our most satisfyingly consistent SFF authors, and I look forward to the rest of this series.