You hit the nail on the head with that, "this isn't what I signed up for" feeling. It was quite an adjustment to accept Claire and Jamie's new age, along with the new characters (Brianna, Roger...pretty much everyone in the future). I thought that since they weren't close to my age anymore that I wouldn't be able to relate to them as well as I had. I was also afraid it would make their relationship less exciting, adventurous and passionate.
I was so emotionally attached at this point, after the first few chapters of DIA I almost put it away. So I broke and had to ask my mom if it was going to get easier to accept (she read the series years ago). She said their relationship still had fierce passion and desire (if not even more than it did before) so not to worry there. But it was also as if no time had passed between them at all. They were still just Jamie and Claire....timeless. She was right, and I couldn't have been happier to be wrong. There was still a wonderful sense of unfamiliarity that excited me with each exchange because they had brand new experiences and physical traits to reveal to each other. It was a dynamic so brilliantly executed. It was strange, but made perfect sense.
The series is like a puzzle that doesn't give any clues as to its final shape, but the pieces fit so perfectly in the end that you're sitting there wondering why you didn't see that coming, or want that to happen, or absolutely neeed that to happen.
So, in the end I pushed through the "future sections" and trusted that there was something amazing in store for me. I mean, there had to be. I was only on the 2nd book!
I'm currently on Drums of Autumn, page 133. Once again, I'm questioning the pace and direction of the story, but I'm learning over and over to just have faith in Gabaldon's storytelling. Absolutely everything she takes us through and shows us has a reason, and the reasons are always, always worth the patience it took to stay with the experience every step of the way. Ok, now I'm motivated to get through this boat ride that's headed to Aunt Jocasta's.