This is the 5361st most frequent Turkish word.
kitabın
"Kitabın" means "your book" or "the book's" in Turkish, depending on context.
In this sentence, 'kitabın' is used as a possessive form to indicate ownership of the cover by the book.
Kitabın kapağı çok güzel tasarlanmış.
The book's cover is beautifully designed.
Here, 'kitabın' (possessive affix '-ın') changes to 'kitabını' (object affix '-ı') when acting as an object in the imperative sentence.
Kitabını masanın üzerine koy.
Place your book on the table.
In this case, 'kitabın' is in possessive form showing that the rich content belongs to the book.