1: A Well-Lived Life - Book 1 - Birgit by Michael Loucks One of the best stories out there. It finds a great balance between plenty of sex scenes on one hand, and an actual compelling narrative on the other.
I'd favorite the entire series but I'm just putting Book 1 on the list as a proxy for the rest.
2: A Fresh Start by rlfj An excellent tale which combines a mixture of time travel, alternative history, compelling human narrative and sexual action into a story worth reading.
3: Graduation Trip by Janet Fremont This story, told from a female perspective, somehow resonated with me (male). It gave me a better understanding of what women think as a relationship evolves and progresses into increasing intimacy.
4: The Three Signs - Book 0 - Background by William Turney Morris A series of books that starts off with a lot of action, but then mellows into a narrative. Much like life itself that way. An excellent read, especially for those who want something less Ameri-centric.
5: Variation on a Theme, Book 1 by Grey Wolf Not just another cliched do-over story. This one explores the evolution of human relationship as well with both male and female protagonists. Still in progress but I read every update religiously.