كِتَابُ الطَّالِبِ جَدِيدٌ — The student’s book is new.
كِتَابُ: nominative mubtadaʾ and muḍāf, made definite by its genitive complement.
الطَّالِبِ: genitive muḍāf ilayh.
جَدِيدٌ: nominative khabar.
Definiteness does not require al- on the head noun; proper names, pronouns and definite iḍāfa constructions also qualify.