Evangelion 1.0 You Are (Not) Alone (ヱヴァンゲリヲン新劇場版: 序) is the first installment in Gainax's "Rebuild of Evangelion" which will eventually comprise four films. It's not a reboot or even a re-imagining so much as a visually refurbishing of the original. The original being Neon Genesis Evangelion (新世紀エヴァンゲリオン) ,which is, of course, a watershed anime mecha series that sparked almost as much controversy (and confusion) as it did commercial success.
Evangelion takes place on an Earth devastated by a catastrophe known as the Second Impact. Humanity is huddled into cities such as Tokyo-3, where they are assailed by bizarre, lumbering monsters called Angels. Protected by something called an AT field, the creature proves impervious to conventional weapons. Only mecha like Evangelion Unit 01, deployed by the Nerv organization and reluctantly piloted by young Shinji Ikari, can hope to fight back.
What are the Angels and why are they attacking? Why has Gendo, the commander of Nerv, press-ganged his son into service? And what's with all the religious symbolism, anyway? The answers to these and other questions were slowly revealed (more or less) over the course of the initial series. This new version, which covers the events of episodes 1-6, sticks very close to that story. So close that not only are entire scenes reproduced but Shinji-kun still listens to music on a cassette tape player. Which is not to say there aren't changes, just that this is largely faithful to the original (at least so far.)
And if that original tended to be opaque and even cryptic, this rebuild tends to be too terse. Character arcs are compressed to such a degree that they begin to deform, so that instead of slowly unfolding they are abruptly revealed. This is largely the result of cramming six hours of material in to a third of the time-span and is therefore to some degree unavoidable. But it means that a lot of NGE's nuance is being lost, and that subtlety was what helped make the series outstanding.
So why do a "rebuild" in the first place? The changes are largely cosmetic and don't seem to be adding much beyond eye-candy. The best you can say is that this will attract younger viewers who might otherwise be put off by the aged graphics of NGE. But people that shallow aren't likely to appreciate the story anyway, so what's the point of that? Maybe I'm cynical, but I just can't help see this as a callous attempt to squeeze more money out the Eva franchise. I wouldn't suggest avoiding these new movies, and I'll probably watch the rest myself, but as of now I can't imagine them as a substitute for the original.
Edit: OK, I realize my math was way off and episodes 1-6 ran 2.5 hours, not 6. But I think my point still stands. They're jamming 150 minutes worth of material into a 98 minute film and some things are getting squashed. I'll use a calculator next time, I promise.