This is from my all-time favorite reviewer on Goodreads, Eric Allen. He's a writer as well. This "rule" really struck a chord with me.
He lists some examples
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What do you all think of this "Four Chapter Rule?" I personally like it; I prefer the plot to get going ASAP with a smaller amount of setup. I've kept it in mind during my writing as well
By the time that you get four chapters into a young adult book you should know the setting, the characters, and have a pretty good idea about what is in store for them. You should be thoroughly invested in the plot, and actually WANT to continue in it. SOMETHING interesting SHOULD have happened, because young people typically tend to lose interest quite quickly if you don't grab them early with something they care about. You should hopefully be connecting with the people you're reading about, perhaps thinking that they seem a bit like you. You should be excited to discover what happens next. The plot should actually be going somewhere by this time instead of puttering around, running in circles chasing its own tail to no point or purpose.
He lists some examples
In Harry Potter and the Philosopher's Stone, by chapter four Harry has had his parents murdered, been raised by people who hate and oppress him, and has discovered that he is a wizard and been accepted to Hogwarts to learn magic. His character and plight have been well introduced by this time, and his hopes and dreams are very clear in the reader's mind. Though his plight is played for comedic purposes, we still FEEL that it IS plight. We've gotten a look at the wizarding world and the tenacity of the owls that deliver their mail. By this time, we know what the book is about, and we know what makes the main character tick.
In Jonathan Stroud's Barimaeus Trilogy, book 1: The Amulet of Samarkand, by chapter four Nathaniel has summoned the demon Bartimaeus and bound him to his will, and Bartimaeus has stolen the Amulet of Samarkand for him. By this time we've been witness to quite a bit of Bartimaeus' sarcasm and wit, and quite a bit of humor to make him rather lovable and we feel his plight as a slave to his human master. Demons and Magic, and a lot of how the world works have been explained to us by this time through the comical rantings of Bartimaeus.
In Garth Nix's Abhorsen Trilogy, book 1: Sabriel, by chapter four Abhorsen has brought a dead infant back to life, Sabriel does the same for a dead bunny. Sabriel is contacted by a being from Death that gives her her father's sword and necromancer's bells, giving her a message that he is trapped by one of the Greater Dead. Sabriel leaves her school to head from the world of technology to the world of magic where she is from to rescue him. We are are shown how Death and Necromacy work. We are shown the wall that keeps the two worlds apart from one another, and we discover that many things are going horribly wrong on the other side of the wall. We've gotten to know Sabriel by this time. We know her reluctance and fear, but also her determination to save her father and prove herself his worthy heir.
In John Flanagan's Ranger's Apprentice series, book 1: the Ruins of Gorlan we've already seen the Dark Lord plotting vengeance and raising an army of nightmare creatures. We've been introduced to the characters and their likes and animosities toward one another. We've been given the mysterious Ranger Halt and his slip of paper given to the Lord while he decides Will's future profession. We can feel Will's burning shame at being turned down for battle school, the only thing he's ever wanted in life, because of his size, and his curiosity over what the mysterious Halt might have to say about him, and what is written on the paper. We've already seen that he is not afraid to defend himself against people twice his size, and that he is naturally good at climbing and sneaking. We want to know why Halt seems to have an interest in him, and what his fate might be after being denied every profession he hoped for.
In Brian Jacques' Redwall by chapter 4 (which, by the way is only ten pages into the book) You've been introduced to the villain, the protagonist, the love interest and the mentor. You've gotten to know that the orphaned Matthias does not fit in amongst the others at the abbey. He yearns for adventure and something more than the quiet life of devotion to others that he has been raised to. There is a build up with a festival planned and the villain setting his sights on Redwall Abbey. You just KNOW that these two events are going to coincide and go horribly wrong, and you can feel anticipation building with each page that you turn. And might I remind you that all of this was set up in only TEN PAGES! TEN PAGES and Redwall is already a more compelling, and better set up story than The Demon King, and it is a book about MICE!!!
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What do you all think of this "Four Chapter Rule?" I personally like it; I prefer the plot to get going ASAP with a smaller amount of setup. I've kept it in mind during my writing as well