This is the book to save the world. Nothing has been held back. However, with all this information, the Cahills can only hope to defeat the Vespers.
For the past five hundred years, the Cahills have been silently changing the world. Their desperate hunt for the 39 Clues lies behind some of history’s biggest enigmas—the curse of the Hope diamond, the race to summit Mt. Everest, the wild life and death of Harry Houdini. And now—finally—the secrets are out. With an introduction by Rick Riordan, The 39 Clues: The Black Book of Buried Secrets reveals the shocking truth about history’s most notorious family, including:
- "How the Black Book Came to Be" by Rick Riordan
- The Five Branches' Founders
- The Five Branches' Top Agents
- The Five Branches' Hot
- The Four Branches' (excluding Madrigal) Tricks and Tools
- Other shocking information:
- Arthur Trent's close ties with the Vesper
- The Kosara's ties with the Vespers
- Also it is revealed that Damien Vesper betrayed his best friend Gideon.
- There is a gold ring mentioned in the book that will be vital to the story and may be what the Vespers are after.
- Amy and Dan went to Grace's bank and left a recorded voice message to Jonah saying, "They found us, they're coming." The message is most likely referring to the Vespers.
- Morse Code (page before Introduction): NEVER FORGET THE MOROCCO ATTACK
- Madeleine's Portrait (page 24) – 12/4 is 3, so A = 3: FIND THE SAFE DEPOSIT BOX
- Page 31: PROTECT GOLDEN RING
- AGENT UPDATE: Amy and Dan Cahill (page 39) – A=Z, B=A, C=B, etc.: KEEP GIDEON'S GOLD RING SAFE
- Founder Archives: Winston Churchill (page 58): A DEAD LUCIAN DUKE IS STRONGER THAN A LIVE TOMAS KING
- AGENT UPDATE: Ian Kabra (pg. 72) – ignore letters R, A, X, N, Y, E, S, Z: DOOMSDAY
- Flag Code (page 86) – key on Page Before Introduction: THE KIDNAPPING PLOT
- Spy Penny (page 86; same picture on Card 176: Spy Penny): WE SEE ALL
- Page 102 – first letter of every word: NELLIE IS A TARGET
- Founder Archives: Annie Oakley (page 131): PROTECT THE SERUM AT ANY COST
- JONAH'S JOURNEYS: ANTARCTIC EDITION (pg. 154) – Small words in the CREDITS section: JONAH KNOWS WHERE IT IS
- Founder Archives: Raoul Lufbery (pg. 165) – "Offset13" means move 13 letters forwards: CLUE MOVED FOR SAFEKEEPING
- Page 173 – Key in clock at end of book: DAN IS A TARGET
- Ekaterina Crest (page 187): DANGER! DANGER!