13 reason why as the title suggest can be best connected in season 1 and 2. When Hanna had her 13 reasons that motivated or rather forced take a drastic step. After this Season 3 is just about missing persons story and season 4 is amazingly boring.

If you really want to enjoy this series then stop after season 2 and you will have some points to ponder. Otherwise season3 and 4 bores so much that you may want to skip a lot of episodes.