I think other reviewers are missing something very important. This is not supposed to be new material. Rehashing is okay once in a while I think.
This is a partial retelling from a different perspective for those of us that cannot get enough of the slimy goodness that was in the parent story ever. And they were good highlights (without giving spoilers).
After all, until we can get the second season complete enough to binge, we need something more that the OVAs (which were likeable enough).
Just my $0.02 worth.
Of course, your mileage may vary. But I was happy enough for what it was.