The anagram is reindeer.
lights and slight
These letters unscrambled spell the word reindeer. The next longest words have seven letters and they include needier and nerdier.
"The 39 Clues: The Black Book of Buried Secrets" provides hints and codes to unlock the various online games and puzzles associated with the series. To solve the codes, carefully analyze the clues given in the book, pay attention to patterns or encoded messages, and cross-reference with other books in the series for additional information. Utilize problem-solving skills and critical thinking to decipher the hidden messages and unlock the secrets within the book.