Should ninahitaji vitabu juu ya siasa be accepted too?
that means 'I need books because of politics'.
Another way to say it would be 'Ninahitaji kununua vitabu kuhusu/vinavyohusu siasa'
I like your suggestion: Ninahitaji kununua vitabu vinavyohusu siasa.
As for juu ya, it seems to have so many meanings in different contexts, someone could write an entire Note about it. :)