The second installment in a trilogy, if you've not seen the first film, you may struggle to get to grips with who the characters are but, given 20 minutes, you won't be worrying... actually, it may even make this more fun, since one wouldn't know of the visual treat to come.
What's good about The Four 2 is that, though it jumps straight into both the story and action, it doesn't leave gaps like the first one did or leave the viewer wondering what was the point in certain scenes; instead, it filters out minor players to make for a more compact viewing, and with the main plot events coming via the actions of characters introduced in this film, it works almost perfectly as a stand-alone product.
With a plot designed to intrigue the viewer as to whom is lying and about what, it's difficult to reveal much, but it was novel to see such tools introduced into a sequel, as in-fighting amongst team members would have come far more naturally than the forced time-fillers that took part in The Avengers or the awful dog "joke" that cued the bout in the Part I.
There have been some who complained that the ending was just a set-up for the third part, but really, it isn't - all questions are answered and had I not known that there was a Part III to come, it wouldn't have ruined the ride for me in any way.
Enjoyable.