"I have more books."
Translation:मेरे पास ज़्यादा किताबें हैं ।
zyada is used in comparisons. don't require an adjective. for example, i have more books than him. aur is more than currently. what is not clear here is the context. is it simply more books because i went out and got more books, or is this sentence a reply to "who has more books? you or Raj?", in which case it would be a comparison. in the former case i would think to use aur. but would be great to hear a native's take on this.