] Catherine's sincerity catches him completely off guard and he finds that he enjoys it. He's beginning to get hooked and he doesn't even know it yet.

I really don't think he's "beginning to get hooked." I think his interest in her at the beginning both conciously and subconciously totally platonic and friendly. He probably knew he was her only male acquaintence in Bath besides Mr. Allen and didn't mind being kind to her and seeing her around, but is rather disinterested. There's a specific point in the book where I feel he first starts to form an attachment.