"Being king wasn't the beginning of a story, it was the end," muses Quentin, the hero, at the beginning of Lev Grossman's fantasy novel "The Magician King" (Viking, 323 pp., $26.95). "This was the happily ever after part. Close the book, put it down, walk away."

It's an unfortunate start for a book that often feels unnecessary; a sequel to a book that seemed complete. "The Magicians," Grossman's 2009 coming-of-age tale, saw Quentin through late adolescence into early adulthood by means of a Hogwarts-like magic school somewhere in upstate New York. A brooding teen who loves fantasy novels and is obsessed with magic, Quentin doesn't find his niche until surrounded by other young magicians. By the end of the first book, he's on his way to the magical land of Fillory — a place he once knew only from books — to rule there as king.

Heavily influenced by J.K. Rowling and C.S. Lewis, but with a sardonic, contemporary lilt of its own, "The Magicians" was a lively, addictive read. But its sequel "The Magician King," with Quentin as a glib monarch in a land far, far away — squint and it looks like Narnia — struggles to find its bearings. The new book has touches of the first's trademark wit (Quentin finds, while on a quest in Fillory, that it's hard not to sound like he's reciting a Monty Python sketch) but less of its likability, as the sardonic but vulnerable teens have become snarky, somewhat remote young adults.

Grossman further hampers the pace by telling two stories simultaneously, constantly interrupting one to return to the other. Quentin and his friend Julia (a queen of Fillory) charter a ship and embark on a journey — which takes them unexpectedly back to Connecticut, where Quentin finds that "reality was proving to be a whole order of magnitude more complicated and less savory than he even remembered." Along the way, we're also told Julia's history: Rejected from the magic academy Brakebills, she learned her art through a grittier path.

Veering back and forth between its two stories, even as it careens from location to location in the real world and back again, "The Magician King" is crammed with plot — but much of it races past, leaving little impression behind. There are lovely bits here and there — the moody Julia picks at her food "like her body was an unloved pet that she was being forced to baby-sit" — that remind us that Grossman is a fine writer, but perhaps needs fresh material. Ultimately, this fantasy tale of a slacker king feels a little, well, slack.

Moira Macdonald is the movie critic for The Seattle Times.