Or: How NOT to write an ending
So let me begin by saying I'm a huge fan of the author David Weber. His bestselling Honor Harrington books are a lot of fun, and his Safehold series is a neat twist on Authurian Legend plus "Technology is Magic".
So, that being said, his latest book Out of the Dark was something I was interested in. The basic gist of the book is Aliens come to conquer Humanity, succeed, then have to hold the conquest. Unfortunately for these aliens, every other race they've conquered has only had access to rudimentary black powder weaponry - not F-22s and Abrams Tanks. Needless to say, despite vaporizing every single nation capital and military base in a preemptive strike on the planet, Humanity gives the aliens heck.
Overall, the book is a lot of fun. Weber manages to capture the frustrations of the Alien Conquerors quite well as they're forced to adapt to new situations and the Human Resistance is comprised of some likable characters.
Now we come to the climax of the book. The aliens have gotten fed up with trying to subjugate Humanity (Apparently, out focus on Family is a foreign concept to the rest of explored space) and decide to just build a bioweapon to take us out. Their initial attempts at getting test subjects gets waylayed by the Resistance in North America, so the Aliens move their operations to the quieter regions of Romania, where a group of Romanians and displaced American forces are building a small but stable community out of the surrounding mountain villages - to the point the Romanian in charge is off discussing mutual defense and trade possibilities with other villages when the Aliens hit his home enclave.
The defenders give a good go, but are ultimately vanquished and the citizens of the village rounded up and taken to this base for testing. Keep in mind, the book has by this point established this base as home to not only the mass bulk of the Aliens Air Lift capacity, but also "Neural Educator" devices, that Humanity appearently works well with and gives them instant access to "Modern" information of an entire Intergalactic Star Empire and a Confederation of planets.
Needless to say, Romanian leader guy is pissed and vows vengeance.
Now at this point in the book, it seemed fairly cut and dry what was going to happen. Romanian was going to use that Mutual Defense Treaty to whistle up a Army, they were going to overrun the alien base, gain access to both the aliens air lift capacity and the Neural Educators, and in short over take the fight to the flagship, conquer the fleet, and yay happy ending.
That's not what happened. The base is taken out yes, but without a single alarm being raised and only eleven shots being fired. Everyone on the base is killed, and the test subjects freed. Video Feeds are erased, and the hardcopy backups are taken.
No big deal. The Romanian's past has been rather mysterious but he and his men have all been established as being rather bad ass. Probably special forces.
Two more bases get hit in the same manner, one in North America. At this point, I'm getting confused - as the aliens never mentioned any missing shuttles.
I'm going to tell you the "twist ending", simply because it's too stupid to even be considered a spoiler.
The Romanian and his men? They are VAMPIRES.
Vampires Save Humanity.
Not only that, but the lead Romanian dude? He's Vlad Drakul himself. Dracula saves Humanity!
Up till this point in the book, absolutely nothing was pointing at a supernatural direction. It had been all strictly sci-fi from this point until it's arbitrarily revealed that one of the major secondary characters is a flipping Vampire.
Seriously. It's not like Weber had written himself into a corner here. He had all the pieces for a very sensible (well, sensible in Alien Invasion Story terms) conclusion that worked in the confines of the universe established without resorting to bringing in Bloodsuckers.
And I stress again, this isn't something that is alluded to. Sure, Dracula has a few lines of dialogue in the book where he's cribbing from Boris Karloff for comedic effect with the Americans and when he's discussing Vlad the Impaler while doing some psychological warfare to dead Alien Troops...but absolutely nothing even so much as hints this guy is friggen Dracula!
This is probably the first book I've been disappointed with in a long, long time. Such a stupid and random way to end the book.