It's interesting how this question comes up so much. For other historical fiction authors like Kate Quinn or Beatriz Williams, the books are more tightly serialized, so order matters more. With Kelly, it's different. The link is spirit, not plot. So you're really asking, 'What is the correct order to absorb a particular spirit of resilience?' And to that, I say, spirit finds you when it needs to. Start anywhere.
Wait, are we sure 'Sunflower Sisters' is part of the same 'series'? I know it's about the Woolsey family, but it feels so thematically distinct being set during the Civil War. I consider 'Lilac Girls' and 'Lost Roses' the direct pair, both dealing with 20th-century wars in Europe. 'Sunflower Sisters' is more of a spiritual prequel. So for the WWII-centric question, maybe just focus on the first two? The order for those is crystal clear: 'Lilac Girls' then 'Lost Roses'.
Oh, good question. I think it's 'Lilac Girls'. Yeah, pretty sure that's the one with Caroline. The other books came later and expanded the family tree backwards in time. I liked 'Lilac Girls' the best out of the three, honestly. The later ones felt a bit more like she was stretching to fill out a franchise, but the original had a raw power to it. The research into the Rabbits, the women experimented on at Ravensbrück, was just devastating. Caroline's real-life advocacy after learning about them is what drives the whole narrative.
Has anyone else found that the perfect reading order might actually depend on your personal entry point? I stumbled upon 'The Cloud Roads' in a used bookstore, fell in love, and then devoured everything else she wrote. Reading her older Ile-Rien books afterwards felt like discovering the fascinating early drafts of a master storyteller. I wouldn't change that experience. If I'd started with the more polished, tight pacing of Murderbot, I might have been less patient with the denser prose of 'The Element of Fire'. So maybe the best order is the one that matches your current mood: fast-paced, humorous sci-fi? Murderbot. Unique, non-European fantasy? Raksura. Gritty, gaslamp fantasy mystery? 'Death of the Necromancer'.