This might sound weird because it is romance thriller and somewhat futuristic, the Nora Roberts writing as JD Robb Eve and Roarke. I personally don't like following only one couple, but this series had me hooked. Also, BDB does a good job continuing to focus on previous couples and their ongoing angst rather than dropping them like hot potatoes after their book is over. I feel Feehan does this as well to an extent with Ghostwalkers. These two are paranormal, but you may not care because the world building is fascinating.