The Magicians succeeds because Grossman tells a compelling story with psychological depth and great pace and verve, but it seems to me that it is based on two conceits that could have stood independently as novels in their own right, and somwhere between these two strands it leaves a central concern of the novel unresolved.
In the first place, The Magicians is plainly a Harry Potter for adults, replacing the magical boarding school with the magical college, and hence teenage angst with early-adulthood self-realization. Of course the young magicians are also college students, but here they get drunk, sleep with each other for the wrong (and right) reasons, suffer identity crises, ennui, career doubts, and generally fumble their way towards adulthood. Grossman captures their competitiveness and anxiety nicely, recasting apprentice magicians as essentially the top-tier of ivy-league students on competitive scholarships. The risk here (as it is in Harry Potter) is that the magical education systematizes and hence literalizes magic, turning it from an art to a craft, from a technique to a technology. Fortunately, Grossman mitigates this by revealing that there are depths beyond depths in the magic his students explore.
In itself, this advanced Harry Potter, the dealings of a hidden class of magicians in upstate New York would be intriguing, but here Grossman avoids engaging in this by introducing a second, though not unrelated strand.
This conceit is one of adult entry into a child’s world of wonder, specifically a faux-Narnia named Fillory. Here, adults with adult concerns attempt to discover and remain in a world of essentially childish magic and wish-fulfillment. The corollary to this, of course, is that one must be careful what one wishes for.
My main dissatisfaction with The Magicians is that when Grossman moves his characters from the subtle conflicts and perplexities of upstate New York into the childishly fantastical world of Fillory, he fails to answer the question that arises so compellingly for the graduate magicians: what is magic for? In mounting the quest into Fillory, he demonstrates that magic and fantasy of themselves cannot bring happiness any more than money or success, and that the regression into the child’s fantasy world can have destructive outcomes. Where magic comes from can remain a mystery, but how to use magic, and how to use it for the good, remain unanswered, and by the end Grossman seems to waver awkwardly between the possibility of renouncing magic altogether and the open-ended conjuring of higher, stranger planes of fantasy, a little like a Dungeon Master seeking even wilder adventures for his already over-powered players.