It's better to think of this as another anime episode rather than some highly anticipating OVA. It's because there's not much action in here. Nevertheless, I still scored it 10. Why? It's because I strongly believe this is an important fragment in the entire story of Shingeki no Kyoujin.
You might wonder or it might be important to know what's in it for you when you watch this. There are 2 things I could give you right away. First, another discovery about Titans that would put a piece of a puzzle in your mind if you already have a theory how Titans exist. Second, another portrayal of soldiers' life and personality particularly Ilse (you'll know her when you watch this), Hanji, and other Corps.
STORY: It's a piece of a puzzle in the entire plot of the series so it's a must watch too although you have to bear in mind that there's a little action here.
ART: I have a feeling it's kinda better than the series but not so sure since I've just shifted from streaming to downloading several months ago.
SOUND: It's neutral, suitable for the scenes. The theme songs are the first opening and ending of the TV series and are inserted just like how it is in TV.
CHARACTER: The characters you've seen remain the same as how you know them in the TV series.
ENJOYMENT: I enjoyed it not because of its battle scenes but because of watching another episode of the series. You wouldn't know how it feels if you're just the type who wants to watch coz of its popularity or just to have something to brag about.
OVERALL: I can't say this is a superb OVA but if you want to know more about Shingeki no Kyojin and want to be refreshed of the story while waiting for a sequel (yeah, I'm also assuming for a sequel) then definitely you should watch this.
