I watched the first episode of The Leftovers when the series debuted and found it intriguing but not that engaging. So I gave up on it until, many years later, I read an article about how the series turned itself into one of the best series ever in season 2. After after finding this is the general consensus, I decided to check it out.
And yes, season 2 of this show about the aftereffects of a day where 2% of the population is riveting. It's this insane, intense, mysterious thing that keeps you off-balance. It was like a whole new series (be warned, you'll need to find a guide to the characters if you start on season 2; there's a lot you'll be wondering about).
Season 3 is also good, although in a different way. The series actually gets nuttier (telegraphed by the strange collection of opening-credits songs). It's a weird shift, since season 2 was pretty emotionally intense throughout, but it generally works.
Much of the power of the series is that it never lets you be sure of anything. There was one supernatural event years before that freaked people out, but the supernatural events in the series itself can be seen as fakes or hallucinations. Much of the series concerns what we believe and how we choose to believe.
There are some things I am not completely sold on. 2% of the population would mean a lot of people wouldn't have been directly effected, and people really do adapt pretty quickly to horrific disasters, but in the series everyone is traumatized for years and everyone's lives is centered around this single event. I don't find this entirely realistic. The third season centers on the belief that something big is coming that seems pretty random. And the ending ... well, it's consistent with the series, but it ultimately feels a little unsatisfying.
But overall well worth watching.