At the moment, Eva Luna is winning since ties are resolved by the first to get its votes, but I'm not sure if that's accidental since the votes were possibly cast in order listed in the first post.
I hardly know how to vote! They are all three (well four but I'll keep it to the three already voted on) equally appealing to me and each so different. One of you expressed a particular interest in Eva Luna while another expressed a particular interest in Unreliable Memoirs, while Observatory Mansions is someone else's nomination (and one of mine won just last month) that sounds very interesting as well.
Also, Eva Luna would happen to give us not only a female author and a person of colour author, but also an author from a country we've never read from yet (actually a country none of the book clubs here have read from yet per Dazrin's stats). On the other hand, Unreliable Memoirs would give us our first nonfiction title since, well, last March, so it's been awhile since we've read one and the book looks very entertaining. Finally, the sample of Observatory Mansions I read was very enjoyable and 'right up my alley' so to speak and I like that it's by a newer author and one I'm less familiar with, and the Goodreads rating for it was just as high as for the other two (they all three are within 0.07 of each other, being 3.96, 3.89 and 3.93 respectively).
All that to say, I have even less of a clue how to vote on this run-off than perhaps ever before, lol.
Knowing that I (probably, I hope lol) won't be the last vote and therefore not casting the deciding vote or vote order, I am still going to vote in a particular order just in case based on what others have said. I'm going to vote for Unreliable Memoirs first since AnotherCat almost gave it two votes and seems keen on it, and then Eva Luna since it would give us a country we haven't read from yet and Bookworm_Girl is keen on it, and then Observatory Mansions. So:
-1 to Unreliable Memoirs
-1 to Eva Luna
-1 to Observatory Mansions
I feel a bit queer (heh, apropos I suppose) about voting for my own nominations first when they're all so equal to me but am doing so since each received particular attention from others. I would be perfectly happy with any of the four in the run-off though, and I suppose I'm leaving it to, ahem, another voter or voters to help make the final call.