I found the most interesting part of the show to be the scenes and interaction with the killers themselves, with the 3 main players recording and profiling the differences.
The problem I have is having seen multiple serial killer documentaries, which have included psychological analysis on each of the most infamous ones prior.... So I find the revelations in the show to be quite muted in comparisson.
Which then leaves the characters themselves and their dialogue and interaction, they're all shades of neutral gray, none are really endearing to me at present.
It's done well, very well produced, it is a nice, quaint show, not aruging the fact.
But all in all i'd still rather go back and watch the actual serial killer stuff, with real interviews from the police/profilers/killers themselves. More interesting without having to take scenes off to focus on a bland agent characters strained relationship with his son or whatever.