。
She has many expensive books.
Literal
She [topic-は] many [genitive-の] expensive books [object-を] is-having.
多くの ('many,' prenominal) modifying 高価な本 ('expensive books'). 多くの is more formal than たくさんの — common in writing and reportage. Note that たくさん is an adverb that attaches directly to verbs without の (たくさん持っている), while 多く normally needs の to modify a noun (多くの本). This contrast is one of the standard 多/たくさん distinctions taught in textbooks.