No specific plot spoilers follow, but read no further if you want to go into the cinema completely unbiased and clueless about what might happen.
The main thing that I can tell you, if you're wondering what this movie is like, is that the look, feel, and tone are very close to those of a Terminator movie back in the day when Terminator movies were good. It also has a bit of a Mad Max vibe, but I think a comparison with the feel of Terminator 2: Judgment Day (a movie for which I have a special soft spot) would make most sense. The experience is more like that than like a standard superhero movie, though if anything Logan is actually a bit darker than T2. The villain, Donald Pearce (played by Boyd Holbrook), even reminded me a little of the T-1000. He's nothing like as personally capable as T2's liquid-metal Terminator, but he's creepy, psychopathic, seems to have infinite resources behind him, and just keeps coming.
If this appeals as an approach to a superhero movie, do see Logan. It's powerful in every way: it kept me on edge, and it made me tear up at times. The performances of the main actors are every bit as solid as you'd expect from actors such as Hugh Jackman (as Logan, a.k.a. Wolverine) and Patrick Stewart (as a very old Charles Xavier, since the movie is set in 2029). However, Dafne Keen steals the show as Laura/X-23.
Warning, though, Logan is dominated by almost unrelenting high-level violence. Even when it does sometimes relent, you always know that more is on its way soon. The result is a suspenseful, involving, frightening futuristic thriller.