From my reading, the books are similar to Harry Potter in that they involve people learning and doing magic, but they involve a much more modern setting and delve a lot more deeply into the human relationship issues involved with growing up as a magic-learning teenager in the US. I'd say the book was way more about people and relationships than magic. (I was honestly more interested in action and magic, but the relationship stuff at least made me feel like I was learning something valuable rather than simply being entertained.)
The first book in the series by Lev Grossman was The Magicians. I was irked that it literally talked about Harry Potter in the text; it's like it was make a commentary on itself in-line. At least it was acknowledging something that should be explicit. While the book was enjoyable overall, I didn't care too much for the modern, teenager-type language, certain jokes and swear words, and at times the general levity with which it's written. Maybe I'm getting too old, but I guess I'm used to "books" using proper, nice language that elevates the rest of the language we use elsewhere; if books fall to match colloquial language patterns, that seems like it can cause a bad downward spiral and lessens the educational value of reading.
While I would've wanted way more magic and adventure (the story didn't feature as much as I expected), I did enjoy the human sides of the story, including the lessons related to trying to run from yourself for some external goal and the problems that creates.
I didn't particularly enjoy certain plot twists that seemed quite random and repetitive (like moving between worlds and coming back for little reason and little plot movement forward). I also didn't like the random introduction deities and all-powerful beings that completely change the plot; it was too much deus ex machina for my taste.
The ending was abrupt and didn't really provide answers (maybe this leaves room for another sequel?).
Overall, I did enjoy reading the books and can recommend them, especially if you're at all interested in magic or fantasy. I guess I had different expectations for them, but that's fine too.