Apologizes for this post being absurdly late. I think that the internet in my dorm has a vendetta against me. Anyway, holy crap was this a good episode.
Of course, that doesn't mean that it made sense. Even in the last episode, the show didn't explain its deeper mysteries, or just hinted at them. However, I don't think that Gainax was trying to pull off one of their famous troll endings by deliberately not explaining things. In fact, Gainax fooled us into thinking that they were up to their usual tricks with the budget reductions of the last two episodes only to bring the big guns in this one. This episode has everything--explosions, daring rescues, last-minute resurrections, and even zombies! It was clear that they were having fun with this, and I welcome the final fantastic return of the beautiful animation that kept me watching this show. However, as enjoyable as it all was, what little plot there was felt rushed, and the half-answers to some of the bigger questions that this series has presented were buried under an otherwise awesome zombie chase/mysterious girl rescue scene. I did really enjoy the surreal quality of that scene, with it changing back and forth from Huey and Dalian running from zombies to Huey trying to get the mysterious girl out of the library only to be stopped by a minotaur. And all this happens after Huey gets shot. He was upgraded to BAMF status sometime during this scene.
Anyway, as an example of one of the mysteries that never gets explained, it was clear that Huey's soul (or some equivalent) was in the library while his body was in the real world. How that worked isn't mentioned. There's also the fact that Dalian is referred to as a doll and it's also shown that she's some kind of real-world counterpart for the girl stuck in the library. This probably would've been something interesting to build on throughout the series, but it's only just now clarified that yes, there's a reason that they look alike. There's also a couple shots of the girl in Greek clothing and a pretty blatant reference to the Pandora's Box myth, but none of it clarifies why she's stuck in the library. Basically, for almost every question they halfway answered, another one popped up. Also, the end of the episode shows (if the fact that Raziel uses German and the general time period weren't enough indicators) that the Professor is most likely a Nazi. And what I've listed here still doesn't cover all of the questions that this episode brings up only to ignore them for a somewhat happy open ending.
Final Thoughts: This show has been an intriguing ride. It started out interesting and ended by still keeping the bigger mysteries in the dark. There's still a lot of material to cover for a potential second season, but seeing how this show took its time to even address those questions, I'm not sure if I want this open ending to be closed definitively. The only episodes that are really required watching are 1, 6, 11 and 12. You can add the homunculus/power rangers episode in there if you like, but the rest of the episodes basically rehash the same material without ever getting to the things that made the series interesting in the first place, namely, the library and how it works. Most of episode eleven is also easy to do without, since Huey's backstory surprisingly added nothing to his character, but since it's the episode that formally introduces Raziel and the Professor, it's included. Most of the problems with the plot have been attributed to the source material, so with that aside, I think that Gainax did its best adapting what it had to work with. With the exception of episodes ten and eleven, the animation has been consistent and beautiful, with extra care taken with the hair and clothes. The lines of movement in the action scenes are spectacular as well. Unfortunately, great animation does not save this show from its unnecessary devotion to its book-of-the-week format when it could've better spent its time developing its characters. Overall, if you're thinking about watching it I highly suggest watching the episodes listed above and then getting into the others if the episodic format does not bother you too much. It's a fun watch but it can be disappointing if you come into it with high expectations of the plot.
Images from NicoNico.com.