Books where the relationship doesn’t hit you out of nowhere?

I just finished reading two books where the MCs were not together until about the midway point, and then suddenly, somehow, they were - no warning, and no emotional build-up. I’ve been left feeling vaguely disappointed and quite unsatisfied. So…I’m looking for a book where the emotional relationship builds slowly, and preferably the sex happens after. Not exactly slow burn (depending on your definition) but more of a story where the emotions are more important than the sex, and the reader can feel the intimacy building between the MCs. Please let it build over the course of one book…I’m not in the mood for multi-book pining or will-they-won’t-they. If they only get together at the very end of the book, I would like there to be either a second book with the same MCs or an epilogue showing how their relationship is progressing (i.e. I don’t want “they got together, the end, bye”).

Bonus if they properly get together/acknowledge their romantic feelings between 50-60% into the book and we get to see the romance progressing even when they’re already a couple!

Any steam level is okay (even closed-door) but please no mpreg, incest, daddy kink, poly. Books between 300-550 pages are appreciated as I read quickly and then feel bereft but shorter books are fine as well!