If You're Reading This, It's Too Late is the sequel to The Name of this Book is Secret in the Secret Series by Pseudonymous Bosch. It was released in October 2008 and features the same characters as the first book. The sequel to this book, and the third book in the Secret Series, This Book Is Not Good for You, came out on September 1, 2009 to Amazon customers and August 31, 2009 to consumers that visited Barnes and Noble that day. The Barnes and Noble version came with an exclusive card telling you a number to call to find clues to the identity of Pseudonymous Bosch.
For 500 years, the secret society of the Midnight Sun has been waiting for the homunculus, the man-made man, to rise, and now the evil Dr. L and Ms. Mauvais are going to throw Cass and Max-Ernest to the sharks unless they tell them where he resides. After going on an excursion with their science teacher, the two are tricked by Dr. L after receiving a note from Pietro saying he will meet them on a ship, from which they barely escape. After finding out their teacher is really Owen, the accent changing member of the Terces Society, they are introduced to the great magician himself, Pietro, who gives them a mission: find the homunculus before the Midnight Sun does. Max-Ernest also finds out that 'Terces' is "secret" backwards. Cass is grounded when she returns home, because she was missing for too long. While on the Midnight Sun ship, Cass and Max-Ernest discover a strange ball, which enables her to hear all types of sounds by putting it to her ear and makes wonderful music when held carefully. Cass also discovers a birth certificate. The name is unrecognizable, thus making Cass wonder if she was the wrong girl the Terces Society wanted. She ignores it, even though it pains her, and continues her mission.
This time teaming up with a new classmate named Yo-Yoji as well as Max-Ernest, the three need to escape the grasp of their parents, and find the alchemist's grave... but Dr. L and Ms. Mauvais have other plans.
Cass - Cass is the female 12 year old protagonist of the story. She is always prepared for any disasters that may occur and carries her bag filled with survival gear. The narrator frequently refers to her as a survivalist. Although she prefers to think of herself as a loner, she allows Max-Ernest to collaborate with her on her investigation of Pietro's death. She has unusually large ears and her real name is Cassandra, although the author claims this is a false name of his own devising. Max-Ernest is her only friend.
Max-Ernest - Max-Ernest is the 12 year old male protagonist of the story. His parents became divorced shortly after his birth because they couldn't decide whether to name him Max or Ernest. Despite this, they still live in the same house divided into two sections (saying that while they dislike each other, they don't want to rob their child of a childhood with both his parents). His parents also have a habit of completely ignoring the other parent - as if he or she is not there- even if it means speaking the same thing the other parent just said. Max-Ernest has a talking disorder that has caused his parents to take him to many doctors. Instead of inhibiting his speech, it makes him talk incessantly until someone stops him. Cass is his only friend. Max-Ernest sometimes acts childish.
Yo-Yoji - A new Asian student at Cass and Max-Ernest's school. Not known by Cass and Max-Ernest, Yo-Yoji is part of the Terces society and has been taught music by Master Wei (also disguised as violin teacher.) Everyone else calls him by his "real" name, Yoji (the author claims to use all false names). he is 12.
P. Bosch - Bosch frequently interrupts the story as its narrator, stating that he shouldn't have written the book, or editing out parts that are too "scary" to write in. He talks about his own life in relation to the adventures of Cass and Max-Ernest. In essence, he becomes his own character in the story.
Ms. Mauvais and Dr. L - Ms. Mauvais and Dr. L are the two antagonists of the story. They seem to know the cause of Pietro's death and are desperate to find his journal, which contains the secret the book revolves around. Once they find out Cass and Max-Ernest have his notebook, they go to many lengths to take it from them. It is also revealed during the story that Dr. L is Pietro's brother after Cass discovers a birthmark of a crescent moon on the backside of his neck that is mentioned earlier in the book. They own a spa called "The Midnight Sun". Ms. Mauvais has lived since the 1800s.
The Dead Magician (Pietro) - Pietro Bergamo is the magician, who was given The Symphony of Smells (a way of seeing the smells) from Ms. Mauvais many years earlier. He also wrote the notebook, that Cass and Max-Ernest found, telling them about how he joined the circus. He had a brother, called Luciano (Dr. L) , who was kidnapped by Ms. Mauvais. Although the narrator often refers to him as "dead" Cass and Max-Ernest receive a note from him in code which they decipher using the code cracker that Max-Ernest owns. Pietro's initials are used at the end of the note.