Though Mikoto only had a major supporting role in A Certain Magical Index, she was incontrovertibly the series' most popular character and is arguably one of anime's most beloved tsundere girls. Thus it is hardly surprising that the spin-off manga series A Certain Scientific Railgun, which focuses on her and her friends (beyond Touma) and their exploits before and during the early stages of Index, also got adapted into anime form and has, in fact, proven to generally be more highly-regarded by fans than Index. While some of the credit for that belongs to Mikoto and her engaging package of powers and quirks, Railgun succeeds where Index sometimes stumbles primarily because it corrects or simply avoids the most prominent problems that plagued Index. In the process it creates a fun and engaging series that effectively mixes comedy, action, and some more serious elements and can stand plenty well on its own; no familiarity with Index is required to appreciate it, although newcomers will miss the occasional cameo from the original series.

The appeal of the series starts with its cast. Largely freed from the shadow of Touma (and thus from being defined purely in tsundere terms), Mikoto shines as a girl who relishes a challenge and has a violent streak but can also be surprisingly down-to-earth, including an affable, low-key demeanor in day-to-day situations, a penchant for childishly cute things (especially frogs), and a fierce loyalty to those she sees as friends. She is also distinguished by her unusual habit of always wearing shorts underneath her skirt, presumably to avoid the random panty flashes that her actions could otherwise bring about. As entertaining as she can be, though, the writing wisely does not have her be the sole focus of attention. Her aggressively lesbian roommate Kuroko, who had minor appearances in the first Index series, gets to show off the full scope of her perversions and teleportation power here, the former of which drives substantial chunks of the series' humor. Completely new characters Uiharu and Saten (they appeared briefly in the openers for Index but that's it) round out the core cast by nicely complementing Mikoto and Kuroko and thus becoming wholly credible friends for an individual whose powers can make her seem unapproachable. The chemistry between the four girls is a delight to watch, and Saten's feelings about being powerless in an environment where most her age have powers drive some surprisingly poignant character development. (Uihara does have a power, but it only comes up once late in the series and is rather lame by comparison to what others can do.) One other character who makes brief appearances in Index – the teacher/Anti-Skill member Aiho Yomikawa – has a more prominent presence in this one, while Index protagonist Touma and the frog-faced doctor pop up occasionally in minor capacities and Index, Himegawa, and the diminutive teacher Komoe have guest appearances. A handful of other new regulars round out the cast, including the seemingly-obligatory Annoyingly Haughty Girl Kongo, but the only real failure is the villain of the final arc, whose sudden transition into Crazed Bad Guy mode is difficult to buy.

Unlike Index, which mostly consisted of bigger story arcs, Railgun predominately consists of one or two-shot stories typically split between the ordinary antics that the girls get into and incidents involving esper power use. However, it does also have a heavier, more involved storyline which concerns the interesting concept of AIM diffusion fields (essentially, the weak energy patterns that espers constantly emanate and how they can interact with each other), a topic which is also central to one story arc in Index but which is developed much more thoroughly here. The storyline happens in two major pieces – one in the first half and one at the end of the series – with some lesser stories being peripherally involved in ways that are not initially apparent. It and a rather odious reference to orphans as “Child Errors” hints at a darker purpose behind the structure of Academy City, a concern that is also raised in different forms in Index, though this series ends before delving too far in that direction. Still, it adds at least a sense of the Big Picture to a series that otherwise has the feel of being composed of side stories.

The other important difference is that Railgun lacks Index's preachiness. To be sure, it does have its fair share of moralizing and discussing rights and wrongs in certain situations, but it never gets bogged down by the pontificating which was the main series' biggest downfall. Saten's involvement with the Level Upper affair, and the fallout thereof, shows what the original series could have accomplished on that front with better writing.

Despite the flashiness of Mikoto's powers, the actual action quotient in this series is low comparative to its predecessor. Mikoto's most dramatic power – the “railgun” shot – only occasionally comes up after the first episode, and only in a few places does she truly let loose. Even so, this series gives a better sense of the true scope of her power than Index does, as its applications are far more varied than just raw blasting power. Kuroko also gets to show off the versatility of her teleportation powers much more dramatically, such as how she can effectively use it to bring a building down if need be. These and other power displays are typically beautifully-rendered by J.C. Staff, and the action components in general are nicely-choreographed and well-animated. Animation elsewhere is solid but unspectacular, although the integration of CG elements is hardly flawless, and fine quality control in rendering is less than consistent. Character designs are a high point, as all of the main girls have fresh and interesting looks with appealing quirks (Mikoto has the shorts, out-of-date socks, and frog phone, Kuroko has the distinctive pigtails, Uiharu has the ubiquitous flower headband, and so forth). Sharp-eyed viewers might also notice numerous hidden cameos from other parts of the franchise and from the series Toradora! and Shakugan no Shana or how the first opener's artistry partly overlaps with the first opener for Index. Fan service is more prominent here, and more than a little daring in places, but even so, this is hardly one of the more fan service-intensive titles out there.

The musical score, which mixes synthesized sounds with light instrumentals, is sufficiently playful, pleasant, dramatic, or creepy as the situation requires but does not distinguish itself. Both its first opener “only my railgun” and second opener “LEVEL5-judgelight-,” which replaces it starting with episode 15, are up-tempo, synthesized songs which display well the series' energy, while a trio of songs by Elisa (The World God Only Knows, the ef series) offer more gently-paced close-outs.

For the most part Funimation's English dub, which carries over all of the performers from Index, is a very solid effort, but it does leave room to nitpick. Brittney Karbowski is a good fit for Mikoto and Cherami Leigh is dead-on as Uiharu, while Alison Viktorin as Kuroko is a hit-or-miss prospect depending how much one finds the very distinctive original performance by Satomi Arai (Peke from the To Love-Ru franchise, amongst others) to be annoying or endearing; Kuroko certainly sounds creepier in Japanese but sounds more convincingly like a young teenager in English. Saten, who has the most emotionally nuanced characterizations, presents a different problem. In terms of acting, Brina Palencia acquits herself just fine (no surprise, since she has proven well-capable in such roles in the past) but her voice does not quite fit; it sounds a little too old and deep for the role, making for a marked contrast with the other distinctly young-sounding leads. Most lesser and guest roles are just fine, though. Translation nitpicks might come in Mikoto being referred to as “Shock Princess” and “Zapper” or Kuroko referring to Mikoto as “Sissy” (it never quite sounds right the way she uses it), but none of them are far off the mark and Funimation's script is generally a little tighter than the norm for them except when replicating wordplay jokes. Curiously, the subtitles leave the names in Japanese order despite them being spoken in English order in the dub.

Funimation is releasing the series only on DVD, but it is releasing both parts simultaneously, including a Limited Edition version of the first part. Extras on both volumes include clean openers and closers and a pair of episode commentaries: the first set has them for episodes 3 and 6 and the second set has them for episodes 17 and 24. The first three feature prominent English voice actresses in sets of two or three, while the last features ADR director Zach Bolton with two additional actresses. None are especially enlightening, but neither are they entirely boring.

Ultimately A Certain Scientific Railgun is a solid, consistently entertaining series with flashes of stronger content. It does not spectacularly excel in any aspect but also has little for major flaws.