The first documentary Louis Theroux made about the infamous Phelps family was terrifically well made and is the best film about these nasty cult members. Now, four years later he returns to hang out with these awful people and to update the audience on their status. The problem is that while it is interesting television, it really doesn't add much to what he already did in the first show. Apart from the defection of a couple of the cult members (and this is no surprise, especially since in the first film they acknowledged that this happens from time to time), there isn't much new--they still spew the same sort of hate and viciousness, though they have, inexplicably, set it to modern music by the likes of Lady Gaga! The total effect is muted to say the least if you've seen the first film--which is all you need to do.
As far as follow-ups go, this one seemed very premature. Just recently, old Fred Phelps himself, the evil patriarch of this hellish clan, died. Seeing what they are doing without him now is what I am curious about and think most viewers would feel the same. Overall, mildly interesting but a severe case of 'been there/done that' when it comes to the subject matter.