Waltraute-san no Konkatsu Jijou (AKA The Circumstances Leading to Waltraute's Marriage) is a short comedy series loosly based on Norse mythology.
The starting point for the series is human boy proposing to a valkyrie. Our heroine gives him a seemingly impossible task after completing which she would become his wife, yet since she is a tsundere, she secretly hopes he actually completes it. But that's just the plot for the first part of the novel (and it does have a definitive conclusion). Truth to be told, the book has no real plot and it only ended where it did because the mag it was released in decided not to publish it anymore.
As for the characters, the male lead (who is just a little kid) is actually a secondary character (heck, he is just referred to as "boy" though the whole book). He is actually very likable. He may be naive, but he has strong determination.
The main character is without a doubt Waltraute the valyrie. Through most of the book we watch her watching the boy from the heavenly world of Asgard where she and a few other mythological characters make lots of meta jokes. As I mentioned before she is kind of a tsundere character of the series, however her violent streak is never pointed at the boy (she just beats the s*** out of everyone else). Speaking of which, whenever he is in danger she completely switches to mama bear mode. Considering she is older than the male lead, I guess it introduces a hint of shotacon, however, regardless of how many ages she have lived for, Waltraute isn't mentally that much older than him.
I found the rest of the characters to be slightly annoying, but except for about 3 of them, they get very little exposition (which is mocked quite a bit in the extra chapter). At the beginning of the series there is a foreshadowing of a harem, but (thankfully) that never came to fruition. My guess would be, that the author wasn't exactly sure what to do with the series when he started writing and he was considering turning this series into a harem at that point, but he didn't follow with that idea.
The shining point of the book is definitely the meta humor and parody. On many occasions there is a big gap in the place where the 4th wall once stood. Although many clichés show up, many of them get averted and characters even comment on that. Many things just happen, without having any details revealed (as when the male lead climbs the huge tree and before you know it he's already pretty high up).
There was one thing that annoyed me in the novel though. And the thing in question was (or rather were) tentacles (which even showed twice). Oh, like many other things in the book, they never get outside of the abstract layer (meaning, that no details whatsoever are given regarding them), but did this book really need them in the first place? Speaking of abstractness, I believe that because of it, this series would not translate well into manga or anime (considering the presence of tentacles, I guess that's a good thing).
To sum everything up, if you want to read a short comedy novel with funny jokes, then this might be a book for you. Just don't expect much in terms of plot or romance, though the little there was of the latter, was rather cute.