I think...having the H/h meet as children, and exposing their non-relationship backfired in this one. I saw the H as an abusive bully in the making, and since he apparently didn't leave home until he was nearly an adult, and since when he shared his prior experiences of the h with his friends, he left out his part, I have a hard time accepting that he really is changed. It doesn't help that once he figures out who the h is, he drops his charming persona and starts verbally abusing her again. His friends never saw them together until after she'd helped them rescue him so didn't see what he was doing.
The h...yes; she was a spoiled brat in a way, but I never got the feeling she was an overbearing witch. More like that when confronted with unpleasantness, she reacted violently. Still, she was just 5 when he first verbally assaulted her (he was 10), and for the next what - 6 years or so? Got to listen to him making unpleasant remarks to her, then when she reacted badly, doing some really awful things. Like, you know, locking her in the attic and leaving her all day (that her parents didn't notice her missing and freak out is surprising).
So I have a hard time believing the relationship, because I have a hard time believing he's truly changed.
I also raised an eyebrow about the h's circumstance. She's 21, and her father has mostly been in a stupor for 5 years. He's in trade, and she's been running the company...for 5 years. Since she was what - 16? Really? And how did she manage to escape the H's dad assuming guardianship over her? Is her cousin her only relative? Things there don't really add up.