[REC] blew me away when I saw it a couple of years ago. In a time when horror movies nowadays seem to be more about shocking and sick imagery than generally scaring the pants off the viewer it was a welcome addition to the genre. So to find out they made a sequel is just fantastic as I thought after the US remake -Quarantine - and the fact that only the US regularly churns out cheap sequels, that it was unlikely to happen.
It picks up straight after where the first one left off and pretty much continues along the same line. Because of this it is never going to shock you as much as the first as you know what to expect, it's even set in the same building as before. So rather than just continuing with the same kind of jumps as before, it adds a lot more to the story that was hinted at at the end of the first.