Behind Her Blue Flame is a prime example of downloadable content done right.
Even when Selvaria was the death dealing goddess during the main story, she has very strong characteristics that just screamed to be given more air time and this downloadable content does that very well. Introduced as a caring and even maybe motherly individual, Selvaria's outlook on her own troops is in contrast to how she appears during the main story. While only a couple hours long, Behind Her Blue Flame reveals a great deal of her true personality and back story that paints her in a much purer light than before. But due to a lack of characters, Behind Her Blue Flame is ultimately limited from moving beyond Selvaria's and Johann's cutesy relationship, which can be a little disappointing.
The gameplay is noticeably different than the main game and can challenging due to some forced limitations. The Imperial units are different to the units in the main game in that they are horrible. This is not all that much of a problem if you are content in playing only the first two chapters of this add on, but becomes a real problem if you are to get A ranks at the end of the mission because of how superior the Gallian units appear to be compared to the Imperials. This results in a handful of overwhelmed units trying to defend their home base from the advancing enemy forces who seem to be able to frequently dodge attacks and generally make it frustrating to get anywhere without abusing saving and loading after an enemy avoided an attack or a unit is killed.
That said, the other limitation is that Selvaria and Johann are meant to work together as a team, although this can hardly be called a limitation. Selvaria is horribly overpowered even without her Valkyrur form because of her scout movement range and her overkill gun called the Ruhm. Obviously, Johann is just a regular engineer who can just barely kill an enemy, but his ability to provide Selvaria with Ragnaid and destroy barricades for the witch proves him to be a real asset in navigating around the battlefield. This team work is one of the most enjoyable parts of Selvaria's mission simply because of how natural and fluid they work together, even if it becomes a little annoying utilizing the less blessed units.
If you are looking for more Valkyria Chronicles goodness, Behind Her Blue Flame provides what it promises - more Selvaria! Regrettably, experiencing the entirety of it may take some trial and error because of some gameplay annoyances, but the core of it is well worth the $4.99 due to excellent handling of one of the most interesting characters of Valkyria Chronicles.