As said in some of the other reviews I read, the first half of the book was way more interesting than the second half. Although I enjoyed aspects, it was not my favourite. But then I tend to read to escape, so was not really wanting a history lesson on the misfortunes of the poor soldiers.
The hints alluding to the other books, surrounding the friends' romances, does make one want to read them. But I don't know if I would actually bother. I definitely prefer the rich gentleman sweeping the heroine off her feet, to the lower ranks.
I also did not enjoy the time jumps, as the characters did not really evolve enough to my satisfaction.