For a small island, Sodor has a huge amount of tracks and trains, and this time, they add more of both. There are a few reused story lines that should be obvious to anyone whose read the books or seen the TV shows, pretty much all the steamie crew get some screen time - to the degree you have a line along the lines of "haven't seen you in a while" towards a couple of lesser used engines - and the standard list of catch phrases and personality traits get an airing in a standard formula.
They also - finally - give screen time to engines who have been mentioned in other stories, but not really had screen time, add a new engine; a new tank engine, whose orders may cause conflict. And a new type of vehicle that's cute and imaginative, even if it could be seen as shoe horned in because of the story.
With Oscar winner Eddie Redmayne and Oscar Nominee John Hurt offering vocal talent, alongside the talented Olivia Colman (who doesn't appear on IMDb, despite voicing a major character), the storyline follows on - if not directly - with a popular franchise; last time it was dinosaurs, this time it's pirates, with many of the clichés that go with that, though while it kept my 19 month old and 3 year old stock still for much of the time (the younger one wasn't happy with the Fat Controller at one point), there are some points about Sailor John that may make adults stop to think. He seems a bit more evil than usual Thomas baddies, especially in regards how he treats Skiff. While there is a back story about the Lost Treasure, there's no real explanation about how he fits into it. And, he can't seem to work when the sun rises...but seems evasive when asked why.
The art work is very pretty - especially the sun rises and atmospheric night shots - and there are a couple of songs; one that sounds like it wouldn't be out of place in Monty Python, the other could fit in a church. We saw the film in a cinema, and there were a couple of great shots that looked even better on the big screen. If your kids like the Railway Series, it's unlikely they'd be too bothered by the story. If you're a parent who has had the previous films on constant repeat, it'll come as a relief to have some variation.