What is the case of كِتَابِي in نَظَرْتُ فِي كِتَابِي?

Noun Case Class 7 — Maqṣūr and Nouns with Possessive Yāʾ

• Nominative with estimated ḍamma
• Accusative with estimated fatḥa
• Genitive with estimated kasra
• Indeclinable