I had rated The Magicians 4 stars. The book has its problems, but it is valuable and worth a read. One reason I gave it a 4 rather than a 3 was because it motivated me to read this book.
The Magician King suffers from the same problems of The Magicians: meandering plot, dissatisfaction and self-loathing, depression, an overabundance of snark, too many pop-culture references, etc. Less aimless drinking though, which is a plus. But just like the first, you could probably shave off about 100 pages of this book.
However the story this time around is quite interesting. I would quibble with the structure a bit, but finding out what happened to Julia, and the ramifications, was worth it (disturbing though it is). Quentin even becomes somewhat likeable by the end.
The big question I would ask Grossman is: why is Quentin in book two is basically the same Quentin as before
all that happened to Quentin at the end of book one (resulting in his hair and everything)? You'd think he would know more about ships at least.