Mission Titanic, Book One, is the first installment of the fourth series within 39 Clues.  You will have had to read the others before this one will make any sense.  The original 39 Clues was quite imaginative in which a prominent citizen of a leading family (leading in financials, political, scientific, athletic, you name it) dies and in her will she issues a challenge.  Each beneficiary, and there are many, may choose between one million dollars cash or a clue which may lead to her entire fortune.  After 11 books, all written by different authors, each book has various family members scouring the world to find clues to the fortune.  I only read book one and thought it was great.  However, Mission Titanic introduces a new family character who has rounded up others to overthrow the new family leaders.  He has given them a clue to prevent an impending disaster.  If they can’t, they lose everything.  First of all, this book goes back to all the younger generation members of the Cahill family and revisits their part of the plot and how they will unite together to solve this mystery.  It pretty much jumps all over the place and doesn’t give the reader a sense of plot or strong characters.  You’ll need to read the other books in the previous three series before this one, and I think it would have been better just left alone.