Finding a good Harry/Hermione story is honestly tougher than it should be. So much of it gets lost in the 'Ron is Evil' trope or makes Hermione a flawless goddess, which misses what makes them interesting. They're two stubborn, brilliant people who've been through a war together; the friction is part of the appeal.
I'd point anyone to 'Unlike a Sister' by MADharmony. It's a post-war, post-epilogue adult story, which I normally avoid, but it handles their established lives and the slow, painful shift in their relationship with so much care. The character voices are spot-on, and it feels grounded in a way most 'Harmony' fics don't. It's more of a melancholy character study than a fluffy romance.
Another one that stuck with me is 'Stages of Hope' by kayly silverstorm. This is a dimension-travel story where a war-hardened Harry, Hermione, Neville, and Luna end up in an alternate world. The Harry/Hermione bond here is built on shared, horrific trauma and absolute reliance, which evolves naturally into something more. It's less about romance and more about survival and healing, which makes the pairing feel earned.
For something completely different, 'Harry Potter and the Lady Thief' is a fun, longer heist-style fic with a confident, thieving Hermione and a Harry who's along for the wild ride. It's lighter and has a great dynamic where they're partners in crime first.