Julian had done more research in his life than he could keep track of but researching into what Izzy thought was romantic was rather different. He noticed a recurring pattern in the novels she liked and was rather confused because what he saw didn't make sense.
Most of the characters that ended up as couples had started out as friends and been through a lot together. Hadn't they done that already? So why wasn't she interested in him?
He hadn't been able to recognize his feelings for her because he had never experienced anything like it before. Was she having the same problem? She had already told him that she thought he was handsome, funny, and so on rather indignantly when he hadn't been able to fathom why anyone would like him in a romantic context.