kitabına

kitabına

"To/for his/her/its book."

Here, 'kitabına' means 'to (his/her/your) book' and indicates the possession ('book of friend') and direction ('to'), derived from 'kitap'.

Arkadaşımın kitabına not aldım.

I made notes in my friend's book.

In this context, 'kitabına' shows loyalty, 'to one's book,' figuratively indicating adherence to one's principles or ideas (with '-ına' suffix for direction).

Kitabına sadık kalan bir yazar kalmaz oldu.

Writers who stay loyal to their books became very rare.

Here 'kitabına' metaphorically refers to rules or guidelines, 'to the book,' and '-ına' indicates adherence to these rules or the act of conforming to them.

Kitabına uyarak hareket ettim.

I acted according to the book.