Fiction - I started reading the Cosmere universe by Brandon Sanderson.
Mistborn Trilogy, Stormlight Archives, and Warbreaker.
Pick 1 - Start with Warbreaker or Mistborn.
I'm new to fantasy fiction and his writing totally hooked me. I think of "hard" fantasy as a puzzle. The world has a unique physics and the plot of the story is based around characters figuring out how to operate inside of those physics... what are the bounds, how can it be manipulated, etc?
What I've loved about Sanderson is the plot turns are never Ex Machina. Every new development fits inside the rules of the world and deepens your understanding of what can be.