Keep it simple. You haven't made any committments. You aren't a jw and are slightly (only) rated better than an outsider at this stage.
Forget the books. Forget the questions. The longer you stay involved the deeper they will get their claws into you.
Tell them you no longer wish to have study. Simple. They may pester for a while, but once they realise you are sincere then those people you had considered good 'friends' will drop you quicker than a hot coal. And no friends is certainly a better option.
Or, you could opt for black sheep's sound advice and tell them to bugger off, leave, piss off, or whatever phrase you may fancy.
Cheeses. Helpful advice at little or no cost.