For people who haven't heard of it, it's based on a novel series by Lev Grossman, with a lot of liberties and deviations. Imagine the conceit of Harry Potter -- an unhappy guy whisked away to a magical school where he learns he's got magical powers and dark magic shit starts happening -- revamped with a more mature, serious, and dangerous polish. The story moves at a lightning pace (to a slightly negative effect as it blazes through the early episodes, but it's ultimately a boon later on), the characters all shine, the tone is consistently balanced between "entertainingly quippy" and "I need to hug a pillow for a while" without dropping into needless gritty edginess, and the effects are great, especially for a show on SyFy.
And the main villain, dubbed "the Beast"... well, let me drop the clip (from the ending scene of the first episode) that immediately sold me on the show the moment I stumbled on it.