Season 1 and 2 were really good. I thought it was entertaining and it kept me coming back.
Season 3 was a bit ... off. It had more than one moment that left me scratching my head with discontinuities and poor story telling.
And then Season 4 was some of the worst television I've ever seen. Characters were drastically changed, forgetting their own strengths, histories, skills. The Lumen was thrown out and then the strongest Hero of the group was painted up like a poodle and then literally squashed like a cockroach. They threw out the mythology of the books and then made the most loathed character in the show the hero in the end.
I'm gonna be avoiding Carlton Cuse shows in the future. Season 4 was a massive and deliberate troll on the fans.