Season two of The Flash picks up down the line from the events of season one, in which Eobard Thawne was defeated due to Eddie's sacrifice. The team has essentially split with Cisco working for the police department, Caitlyn working at Mercury labs, Iris mourning Eddie's death, and Barry trying to singlehandedly take down the various evil metahumans. The big bad is set up early in the season, revealing that Zoom, an evil speedster on a different Earth, Earth-2 is sending metahumans to Earth-1 to take out Barry. Barry is joined by Earth 2's version of The Flash, Jay Garrick, played by Teddy Sears (from the series Masters of Sex) to help Barry take down Zoom. Zoom's identity is kept secret until later in the season, but when he does make his first couple of appearances, he is voiced by Tony Todd.
The season also expands the Arrowverse. First, there is the annual crossover with the parent series Arrow, which set up the cast and storyline of the first season of Legends of Tomorrow and served as a backdoor pilot for that series. Second, later in the season, Barry crosses over to Supergirl, which was in its first season and airing on CBS. That established that Supergirl was on yet another Earth, fully entrenching the multiverse concept which would be key, especially for later crossover episodes. Of course, the show has a ton of twists and turns, and given the multiverse and time travel aspects of the show characters who are dead do not always stay that way. The multiverse also gave a way for the show to keep Tom Cavanaugh (who of course played Eobard Thawne impersonating Harrison Wells as Earth-2's Well, called Harry, comes to Earth-1 to help the team take down Zoom.
For those who get the blu-ray set, the show again looks and sounds great in HD, with the special effects looking nearly seamless. Because the Flash's speed requires using animation, you can tell the difference between when it is Grant Gustin in the suit versus an animated version of the character, but even that blends in pretty well. The extras include deleted scenes, several short behind-the-scenes featurettes, a gag reel, and a half-hour-long panel discussion with the showrunners and cast from the 2015 Paley Fest.
Overall, the season is very good. It is well-written and very well-acted. The season ends on a pretty massive cliffhanger that will definitely have an impact on season three. It is more light-hearted than Arrow, overall, although it does have some dark moments of its own. It also includes a lot of good guest stars including Peyton List, Mark Hamill (reprising his role as Trickster), Aaron Douglas (from the remade Battlestar series), and more. Of course, characters from Arrow appear on the show, and Amanda Pays reprises her role as Tina McGee, a version of the character she played in the 1990 Flash series. So, if you liked or loved season 1, you will probably feel the same way about season two. Since the Arrowverse is now starting to tell intertwined stories within the case or metahuman-of-the-week procedural format, you almost have to watch all of the shows to understand everything that is going on in the others.