The Angel is an experimental film with a capital E, and with a few exclamation marks in there for added effect. An E(!!!)xperimental film, if you will.
It's strange enough that it's hard to even summarise. A figure seems to be continually walking up a huge flight of stairs, and along the way, he meets people (sort of?), or else other scenes featuring other people play out from time to time.
You can read into it what you want, or just take it as a unique, unnerving experience. In that latter way, it works well, and is more engaging than most experimental movies (even if you're like me and don't know what to make of it most of the time).
The music and sound design is really effective, and the visuals are great, especially in the film's final scenes. I might have 2001: A Space Odyssey in the mind after seeing it again last night, but The Angel feels a bit like an hour-long version of that film's final 15-20 minutes. Lots of striking imagery that's hard to define it even comprehend.
All in all, The Angel was a challenging watch, but a mostly solid one.
