The Flash really cemented itself as one of The CW's flagship shows with its second season. This season is really all about time travel, multiple universes and Earths and the ramifications of the events of the season 1 finale. It picks up after the singularity that ended as the season 1 cliffhanger was closed, but we do not learn until about 1/3 of the way into the episode how, and at what cost, it was closed. As a result of the singularity forming, there were breaches to Earth-2 opened all throughout Central City, which allowed Zoom (this season's big bad) as well as a host of other meta humans to come through and wreak havoc. It also provides a way for Tom Cavanaugh to stay on the show as Harrison Wells despite Reverse Flash being defeated and ultimately erased when Eddie sacrificed himself.
I will not say too much about what seems to be the main complaint of the season because to do so would give too much away (it involves Zoom) and while I get the criticism, I think by the end of the season you can see why the writers went the way they did, and it sets up a lot going into season 3. The core story is Zoom trying to kill Barry so he can take Barry's speed. Within that there is still some of the serial case of the week stuff from season 1, more characters (including a new love interest for Barry) and the Arrow crossover episode which essentially set up the story arc of Season 1 of Legend's of Tomorrow. Unfortunately while there was a crossover episode with Supergirl with Flash making an appearance on that show, Supergirl did not appear on The Flash save for a split second shot as Barry was traveling through time.
For those who get the blu-rays, the show looks and sounds great. There are a ton of extras with several behind the scenes and making of features on anything from the plot lines to the special effects. There are deleted scenes for several episodes, two convention panel discussions, a gag reel and the best featurette (in my opinion) a nearly hour long behind the scenes feature on the Kevin Smith directed episode. That episode was the best of the season (again in my opinion) and it was great to get a look at Kevin Smith and the cast and crew discussing making that episode. There is a lot there for those who like going through the bonus material. The only thing that would have been nice are some commentary tracks on some of the episodes.
Chances are if you liked season 1 of the show you will enjoy this one. If Superhero shows are not your thing, or you kind of have fatigue over the genre in general then you will probably not like it. I definitely think the DC Television Universe has far outdone Marvel (aside from the Netflix series) and has really flipped from what Marvel has done in the Cinematic Universe vs The DC film Universe so far. I definitely think it helps to have all the shows on the same network now, with the same producers and the writing staffs being able to collaborate. There is a lot of continuity among the shows so, while they are definitely telling their own stories, they can be tied together into larger story lines. As for the Flash itself, it continues to be well written and acted, and is definitely worth your time.