This movie to me is a transition movie in the sense that you have characters from both the original series and the TNG series. This is the very last star trek movie to have the original tos characters. After this movie, it will be all TNG until we hit the 2009 version of star trek.
This particular movie though is about Dr Soren and all he wants to do is get back to the nexus. Soren's family was killed by the borg. In Kirk's time, Soren tried to get to the nexus and fails. This is also when Kirk is presumed dead after a hull breach, but finds himself in the nexus.
In Picard's time, Soren tries again to get to the ribbon. He meets up with Kirk and gets his help to keep Soren from getting to the nexus. At first Kirk didn't want to, but he did end up helping Picard.
The movie itself is a stepup from what you are used to with movies with star trek. There is a bit more adventure, but not quite up to the TNG standards of adventure. If you love star trek, this movie would be for you.