You could always try watching a YouTube video about differences. If they seem big to you don't read.

No one should give you actual hate that you haven't read something. Teasing sure but not actual hate.

I didn't read the books till about the fifth movie was out? My uncle gave me the last book for my birthday so I got the others and read them. I like the movies, they aren't like a confort thing for me but I still like them and have all on DVD.

It honestly depends on how nit-picky you are on adaptions. If you focus on the tiniest thing it might change your opinion on them, then yeah I'd recommend not reading if you love the movies. But if you're more laid back and don't mind some deviations, some are pretty major, not enough to change the story but enough that it would have been cool if they could have kept.

You may want to start out with novellas, they are books that are longer then a short story but shorter then a novel. Another thing you could do is try sketching out characters, adding more to them as you discover more about them. There are stories that go extremely into detail as well, I don't like those kinds of books because for me they drag but they might be more your cup or tea.

Also you don't have to read just one book at a time. Some people do because they find reading multiple books overwhelming but for me once I get kinda bored with one book I move onto another to read for a while then come back.