Final answer:
The specific text Filius Flitwick required his sixth year N.E.W.T. Charms class to read is not specified in the Harry Potter series; therefore, a definitive answer cannot be given.
Step-by-step explanation:
The text that Filius Flitwick required his sixth year N.E.W.T. Charms class to read in the Harry Potter series is not specified in the books, and thus cannot be answered directly.
The question seems to draw upon themes of magic and sorcery, which are common in studies related to Charms within the Harry Potter universe. However, without explicit information from the source material, it is impossible to provide a factual answer to this question.