I saw the Snowpiercer movie a few years ago and enjoyed it as a free-be on a streaming service (good not but not great, as stated above). I read a lot of books that get turned into movies and TV shows, so I never give any thought to things like keeping one separate from the other (constantly making mental comparisons among media formats is inherent to how I consume entertainment).
With that said, the first episode started to look like it was following the movie pretty closely (Tailies desperate and trying to fight their way up the train cars), but then the murder mystery kicked in, along with the twist about "Mr. Wilford," and it suddenly got a lot more interesting. I don't expect this to be a "peak TV" kind of show, more like passable, if not above average, summer filler.