A masterpiece, and one of just two manga that I've read all the way through more than twice (the other being the very different Azumanga Daioh). Akira is a psychic tale, a cyberpunk story, a gritty urban drama, glorious disaster porn, the fraught tale of two teenage boys and their friendship/rivalry, and, at the end of the day, one of the most influential manga of all time. Without Akira, and without Katsuhiro Otomo, we wouldn't have Ghost in the Shell, or Battle Angel Alita, or Banana Fish, or even Pineapple Army (go look at Naoki Urasawa's art for that and tell me it's not Otomo-influenced). If you have any interest in manga as a medium at all, Akira is a must-read alongside other storied classics like Phoenix, Barefoot Gen, and Nausicaa.
It's also an engrossing page-turner of a manga. The story is well-known: it's the year 2030, long after a mysterious new weapon leveled Tokyo and kicked off World War III. A teenaged biker gang enters a restricted area of Neo-Tokyo and encounters a young boy with the wrinkled skin of an old man. An explosion happens, gang member Tetsuo is whisked away by the government, and the gang's leader, Kaneda, tries to find out what's going on. During his journey, Kaneda encounters gruff and secretive military types, powerful psychics, a government resistance group, shady politicians, and eventually, the one known as No. 28, or Akira, who is the focus of all these disparate factions. Meanwhile, Tetsuo's nascent psychic powers develop thanks to the military's experiments, and he starts to loosen from their grip...
The anime, while more famous than its source material, only covers about 40% of the manga's story, and relegates some major supporting characters, like Nezu and Lady Miyako, to tiny background roles. In addition, both Kaori and Akira are handled very differently, in part because the movie compressed so much of what happens in the manga. In the manga version of the tale, individual events are given more breathing room, and some things that may be confusing in the movie are explored at length. If you watched the movie and are intrigued by the world and the characters, but found yourself frustrated with the story and pacing, give the manga a try.
Most of the characters can be described entirely in a sentence or two. Some, like the Colonel and the Doctor, don't even get proper names. However, the main trio-- Kaneda, Tetsuo, and the tomboyish resistance member Kei-- develop quite a bit of nuance in their personalities and motivations, and there is a lot of chemistry in how the overall cast interacts with each other. There are even some humorous moments breaking up the drama every so often, with these scenes usually involving Kaneda and Kei. The pacing is nicely balanced between scenes of talking (or arguing) and action setpieces, with the biggest and best of the latter pushing Otomo's outstanding draftsmanship talents to their limits. He is a master when it comes to drawing buildings and large-scale sceneries... and their destruction. Some of the best panels, in terms of scale, show tiny human figures being tossed up against massive slabs of concrete and whole chunks of buildings.
There are very, very few weak spots in this manga. I still prefer the movie's ending; the manga's is a little too open-ended and sentimental compared to the rest of the series' tone. The scenes involving Nezu's compound are also a low point (albeit not much of one), where the story slows down considerably and new characters are introduced who, in the end, don't contribute much to the overall tale. However, the payoff at the end of that arc is worth the wait, and the series as a whole is not dragged down by these less impressive moments.
If you consider yourself a serious manga connoisseur, or just a fan of action-packed stories, and haven't read Akira yet, what are you waiting for? There's a reason why it has stood the test of time, and is still so beloved by many, decades after it has ended.