Is it permissible to say "kitābni" instead of "kitābī"?

It is incorrect to say "kitābī-nī" (كتابني) instead of "kitābī" (كتابي), because the nūn al-wiqāyah (نُون الْوِقَايَة - 'nūn' of protection) does not precede declinable nouns that can take a kasrah. Rather, it precedes verbs and some particles and indeclinable nouns to protect them from taking a kasrah, as stated in the Almighty's saying: "Go with this — My book" (اذْهَبْ بِكِتَابِي هَذَا) and "Recite My record!" (اقْرَءُوا كِتَابِيَهْ).