A Certain Magical Index is the eccentric professor of action anime: full of bright ideas, fascinating to watch ... and constantly tripping over itself when it tries to get anywhere. Over 24 episodes, this series plumbs the depths of religious mysticism (historically accurate or not), pushes the limits of cutting-edge science, and displays great visual flair while doing it. But just as often, it ruins the experience with long-winded dialogue and clumsily arranged story arcs. Make no mistake: Index takes viewers on an exhilarating ride, but one that is also very disorienting.

At its best, the series is a whirlwind of mind-bending ideas, taking a simple concept and spinning out a number of unlikely twists. For example, the initial story arc—about Index trying to escape predatory sorcerers—is anything but a basic "defeat all the bad guys to protect the girl" scenario. When the main hero's power is to cancel out everyone else's powers, the very logic of the supernatural-action genre is put to the test: how far can Kamijo go despite having no real skills? The finale of the first arc answers this question in explosive fashion, as Kamijo's all-canceling hand goes up against every magical spell in Index's head. In the series' other marquee storyline, Kamijo goes up against walking science experiment Accelerator, whose ability to manipulate mathematical vectors (which govern the entire physical world) seems unstoppable—until, of course, he meets the ultimate stopper in Kamijo.

Index will also win fans over with carefully concealed mysteries and cliffhanger-driven suspense. Often times, a villain's goal (such as "capturing Index" or "summoning vampires") hides a much more complex motive, and trying to unravel that motive makes for addictive viewing. Even when the mystery is more comical than threatening, like a curse that suddenly makes all the characters look like someone else, the search for truth becomes a tricky, winding path that keeps the real answers hidden until the very end.

However, it's the way those answers are presented—and other relevant information—that ultimately become the series' undoing. As early as Episode 2, Kamijo finds himself caught not in fierce battle or solving a mystery, but standing around having several-minute-long conversations about how magic works in this universe. Or, if not magic, then the science and politics of Academy City, like what makes Accelerator such a big deal and why electricity manipulator Misaka has dozens of clones hanging around. What ought to be an intense, action-packed show keeps getting slowed down by its own overly complex universe.

The layout of the story arcs also leaves much to be desired, as there is no sense of progression over the season. The dramatic climax is arguably reached by Episode 6, when Kamijo saves Index, and everything else is just a repeating cycle of the problem-battle-twist-solution formula. The lackluster final arc says it all: even though it features yet another high-concept idea (can stray ESP waves form sentient beings?), the final battle is a run-of-the-mill brawl, Kamijo shows no significant growth as a character, and a few dangling plot points ("Stay tuned for Season 2!", they're saying) make for an unsatisfying finish.

The visuals in Index are just as inconsistent as the storytelling: fight scenes are often dazzling and well-choreographed, while day-to-day school life looks like the work of the studio's laziest artists. When Kamijo takes on Accelerator, or Index's unholy powers kick in, glowing special effects and dynamic camerawork create a true sense of epic battle. (Funnily enough, some of the comedy moments are also very well animated, such as Index throwing a tantrum.) But whenever the characters have to launch into one of those seven-minute magic theory lessons, the straight-ahead viewing angles and dull backgrounds make the show about as exciting as reading a textbook. Because those scenes take up such long stretches, the lazy (or even static) animation may stick in viewers' minds just as much as the great battles. At least the uniquely designed characters make up for it—their discussions may be long and boring, but their looks are memorable.

Although billed as a series where "science and magic collide," the urban setting suggests a more futuristic bent, and the electronically-infused soundtrack confirms it. Battle music comes in the form of a thrumming beat and dissonant synthesizers, which sound unique but aren't always emotionally stirring. Quieter, more sentimental scenes are set to acoustic piano and strings—a major contrast, but still second in importance to the electronic tracks. The theme songs, meanwhile, rely on the usual formula of an uptempo opening and ballad ending, with the hard-rock sound of the second opening being the most effective.

When it comes to expressing emotion, the English dub has plenty to spare, whether it be Kamijo's determination, Index's childish verve, Accelerator's ruthlessness, or anything in between. Unfortunately, emotional nuance is where the dub falls short, and it often sounds as if the cast is just trying to get the lines out in the appropriate character's voice. Pacing is another issue: as the actors try to match the lip-flaps on screen, the cutting-off or jamming together of certain sentences creates an unnatural effect. And this is even after a fairly liberal rewrite of the script, meant to help the dialogue run more smoothly. Ultimately, the English dub sounds too forced, although the actors do have a looser, more fun time on the commentary tracks that accompany certain episodes.

Putting it all together, A Certain Magical Index really is the ultimate rollercoaster ride. It soars on the heights of complex supernatural and sci-fi ideas, tantalizing mysteries, and no-holds-barred battle—then it plunges to the depths of too much expository dialogue, so-so animation, and the lack of a climactic finale. Maybe this is one of those cases where aiming for the middle of the road wouldn't have been such a bad idea. Certainly, Index is worth enjoying for the things it does well—but it takes some real tolerance to sit through the lousy parts.