I would hesistate to classify this series as romance - real romances are a lot better (or worse
) than this!
To answer your questions -
1. Yup, it does get better. She goes into the more details of the war and associated problems (trying not to give too much away). Subsequent books see the main characters travel to America and we see the start of the civil war. Around book 3, she drops out of the 1st person view, so we get a bit of jumping between the 2 story-telling types.
2. I would say the strength of the series lies in the characters themselves - and since they are married (?!) we will see sex scenes. It's been a while since I've read the books so I can't remember how many, but I do seem to recall that they're not as frequent. But then again, the scenes don't bother me. If you've read Jean Auel's work you'll know that Gabaldon's scenes really help to enhance the plot! I will say that I skipped over the scenes in Wilbur's latest books as he doesn't do a super good job with them (lol).
The books are my favourites because the characters she has created are very strong and as a reader, they pull you into their lives completely.
Book 2 is good, 3 is a little weak (consider it a bridge book) and the rest actually get better. Give Dragonfly in Amber a chance.