Looking for a science fiction or fantasy series that I can really sink into

I have a problem. I struggle to get invested with one off books, because I want to fall into and become deeply immersed in a world for a long time.

I ALSO don't want to risk my somewhat limited personal time to sink into a universe I'm going to only passingly enjoy.

I like longer books, I love exposition, and I also love when authors spend significant amounts of time in the narrator's thoughts, and why they choose to do what they do.

While I enjoy books targetted at young adults, that's my "tv time" kind of content. So not looking for in the vein of Harry Potter, or Star Wars (as great as they are)

Some series I have really enjoyed in the past that have the right je ne sais quoi that I am seeking are "A Dream of Eagles" by Jack Whyte and "The Lightbringer" By Brent Weeks

Notable, I've tried other books by both those authors, and they didn't quite hit the right spot

Generally enjoy Sci-fi or Fantasy. Historical fiction of the right kind works too