Man, I've fallen flat on my face enough times with this to have some thoughts. The worst thing you can do is write each chapter like it's a short story with a neat little bow—readers tune out if there's no forward momentum. What clicked for me was treating every chapter like a promise and a threat. End with a question the reader can't ignore, even if it's just a character deciding to open a suspicious letter. Cliffhangers don't need to be life-or-death; sometimes the tension is in a quiet revelation.
I also swear by the 'checkpoint' method. Every three chapters or so, I make sure a minor thread pays off or a character gets a moment of clarity. It gives a sense of progress even during the slower, world-building sections. If a chapter feels like pure setup, I cut it or fuse it with another. Readers on serial platforms have endless options; a boring chapter is an unsubscribe.
My current project moves faster because I write the first draft with almost reckless speed, then go back to layer in subtle foreshadowing and sensory details. The initial momentum is what keeps me, and hopefully the readers, hooked.