That show is very weird it is un-categroizeable. Things get pretty stale by the beginning of season 2(if you know what I mean, no spoilers). I couldn't finish it after that.
It’s due to CBS’ foolish decisions to reveal the killer and change the format.
Watch S1, then S2 episodes 1 to 14. Then skip to Episode 28 and 29 (last episode). The last episode of S2 is amazing, with an amazing cliffhanger... until S3 appeared 25 years later.