This book was on my sister's to-read list, and I think I know why. Karen absolutely loved the Harry Potter books, having read them to my nephew as he was growing up. At first glance, The Magicians has a similar premise - boy discovers a whole new world of magic, and is invited to attend a school for magicians. But whereas the Harry Potter books were about a sweet, young British boy attending a nice British school for young kids, this book is about Quentin, a horny, mopey, angst-y American teenager from Brooklyn attending a college-level school in upstate New York. There's a lot of college-level antics in this book - drinking, cussing, sexing - that you wouldn't have found anywhere remotely near Hogwarts.
While Rowling's descriptions of performing magic were full of the romantic aspects - waving wands and saying pretty words, Grossman focuses more on the journeyman type aspects of magic; if the teachers at Hogwarts look at magic as painting or sculpting, the faculty of Brakebills consider it more along the lines of baking or carpentry.
But Quentin's education at Brakebills is only the beginning quarter of the book. As a child (and. let's face it, as a teenager) Quentin read over and over a Narnia-esque series of children's novels depicting a land called Fillory. After graduating from Brakebills, Quentin and friends discover that Fillory actually exists, and they set off on a Magical Quest to find it. The remainder of the book relates that quest, and what happens with the friends when they discover that Fillory-of-fiction and Fillory-in-real-life are not necessarily the same thing.
I think Karen would have enjoyed this book, once she got past the disappointment of it not being (at all) like the Harry Potter series. There are some definite "adult situations", and Grossman makes it clear pretty early that these are not cute little kids in a cute little magic school. There are deaths, and hook-ups, and imbibing of various drugs and alcoholic beverages. But it's an exciting, well-developed story complete with Important Messages that make us Think about Life.