Complex sentence: The dangerous book had found its way into the hands of Death Eater Lucius Malfoy who had then passed it to Ginny Weasley in order to discredit her father, Arthur Weasley.
Split into simpler sentences: The dangerous book found its way into the hands of Death Eater Lucius Malfoy. Malfoy passed it to Ginny Weasley in order to discredit her father, Arthur Weasley.