I've not read the book but I thought the series was really dull, and terribly acted. I feel like I've watched/read the trope about the rich, pretty, popular girl who's actually really lonely and had a terrible life, versus her 'nerdy', well brought up friend who never gets the boys and idolises her. I think Tully was actually quite a
crappy person, and not a good friend to Kate at all.
I thought it was weird how they just filtered Kate and Tully's faces and put Johnny in a dodgy wig to pretend they were 20 years younger and then expected that we'd buy some 30 year old in a grey wig was Katherine's mum
I'll probably watch the next season just to see why they fell out, but it's definitely something I switch on for background noise while I'm about the house.