American Wife by Curtis Sittenfeld
This novel is more present day than Nightingale. However, Sittenfeld's prose style reminds me of Hannah's. It is detail oriented without being heavy with detail. It focuses on female character's trials and tribulations.
Winter Garden by Kristin Hannah
This was the first Kristin Hannah novel I would recommend prior to Nightingale's publication. It is heart breakingly beautiful so be prepared for a tear jerker. It is complex and haunting, and one of Hannah's best.
Is there any novel you would add to this list?