No, it really isn't a sequel to Cloverfield. Not at all.

Rating: 7/10 (6 May 2016)

Okay, before I start, a word about the negative reviews about this film. Most of them seem to fall into a category I'll generously label as "It said Cloverfield in the title! WTF!" Said reviews are from people who erroneously assumed it was a sequel to Cloverfield because of the name. It isn't. Nor is it really anything to do with Cloverfield the movie, or that universe. Abrams himself muddied the waters a little and isn't without blame because he called it a "spiritual cousin" to the original.
However, what 10 Cloverfield Lane is, is a movie in the same vein, but not at all alike. A bit like Star Wars and Star Trek are both scifi films, but expecting one to be a sequel to the other just because they have the word "Star" in them is the height of idiocy. Same deal with this movie. You can safely ignore those reviews because the majority of them are written by disgruntled Cloverfield fans.
Now, on to this film. Is it any good, and what is it really about? Well, it is at its heart a thriller of sorts, with a healthy dose of mystery and "what the hell is going on?" thrown in for good measure. With a cast of just three people for the majority of the running time it manages to keep the tension going nicely.
It would be hard to say much more without ruining the movie entirely, but most things are revealed and wrapped up by the end. Whether or not it comes across as satisfying is entirely down to what your expectations are going in and what you are expecting to see (hence my comments about the negative reviews above). If you go in with an open mind, you might just find it more enjoyable and satisfying.
Performances are good throughout, but Goodman is the standout here. Forget his usual lovable rogue routine. He goes to an entirely different place in this film.
The ending is controversial if it isn't what you were expecting, but it is also surprising. I think, ultimately, that using the word "Cloverfield" in the title was an attempt to let potential viewers in on the... unusual and unexpected... ending. I think they wanted to not let the cat out of the bag, but just poke it so it mewed a little and gave people an idea of what to expect. Sadly, as note, some people took it too literally and were disappointed as a result.
That's not to say the ending is particularly good. Everything that comes before it is somewhat cheapened by the sudden descent into... action... that ensues, and it is thematically a seemingly tacked on experience. You could quite literally swap out the last ten minutes for any number of other endings and they would all work just as well (or not, depending on your personal liking). The ending that you get, however, is quite striking.
Altogether though, 10 Cloverfield Lane is a thoroughly enjoyable thriller with a few twists that left me happy I decided to watch it. You could do worse.
SUMMARY: Decent thriller with a name that left too many expecting the wrong thing. Excellent performance from John Goodman playing against type and with an ending that is a Marmite moment for a lot of people. Worth the effort, however, if only for Goodman's performance.