This had such an interesting twist on mpreg. I'm laughing because I'm comparing it to the more mainstream mpreg that I've read. Yanno, because mpreg is such a mainstream trope in and of itself. ;)
Lots and lots of sex here. I mean lots, so if you're looking to get your menage on with a side of alien then pick this one up. It was very relationship and personality driven with less of an emphasize on plot but I found the characters endearing and the master/pet dynamic worked very well.
About the ending. I liked how it ended because it was perfect for how the men were viewed by the Algonquan aliens.