Sarah J. Maas
Sarah J. Maas writes fantasy romance on a scale that's hard to describe until you've read it. Her books are long, her worlds are elaborate, and her readers are devoted in a way that few authors manage to inspire.
She has three main series: A Court of Thorns and Roses, which is her most popular entry point and leans heavily into romance alongside the fantasy; Throne of Glass, a longer epic fantasy series that follows an assassin navigating a brutal kingdom; and Crescent City, which is set in a modern world layered with magic and mythology. All three series are connected in ways that reward readers who go deep into her work.
Maas started writing Throne of Glass as a teenager and published it after years of building an online following. That origin story says something about how she writes. There's a lot of heart in these books, even when they're at their most dramatic.
If you're new to her, A Court of Thorns and Roses is where most people begin. It's the most accessible and it moves fast. Just know that the second book is where things really open up.