Obviously, you'll be playing as Raidou Kuzunoha. You've already said that you know how it plays? Then I'm guessing that you know the combat happens to be action paced this time, and not turn based like in other SMT games. When I had it on the PS2, I actually didn't play it to the end but I played enough to explain some things.
I'm pretty sure that I happened to make it all the way to either "Episode 7" or "Episode 8" before I stopped playing for personal reasons. Anyways, the town you start in feels "old-timey" and has that Japanese look and feel. I actually enjoyed walking around and Raidou's whole outfit and demeanor. He also happens to be a silent protagonist but what am I saying? that happens to be a re-occurring theme in the SMT/Persona series.
Devil Summoner 2: Raidou Kuzunoha vs. King Abaddon, happens to be a lot darker than say Persona 4. It's an actual SMT title (Fun-Fact: They only used the SMT title on Persona 3 and 4 for brand recognition/sales). Furthermore, the "dark" look can be seen in the characters, world and the demon's. This time round, you'll be fusing demon's with a crazy old scientist and a steel cage fueled by electricity.
If you've played an SMT title before, and it seems like you have, you should be expecting the same "feeling" you get in previous titles in the franchise. I've actually been playing SMT IV on the 3DS because I finally purchased a 2DS. Just imagine, walking around and doing battle via Dragon Quest's battle system (First Person View). But that's neither here nor there... There's also dungeons in DS2, but they aren't as extensive as say, Tartarus in Persona 3.
Hopefully I've answered your questions enough to get an idea from of what you're getting yourself into.