Let me start this off by saying a critical statement:
There is nothing wrong with the traditional chapter format for a book!
That’s important to say because some people think that any advocacy for new techniques and new formats in any sort of media is a condemnation of what has come in the past. The normal chapter format is great and I’ve used it for the majority of my own writing. That isn’t to say though that there isn’t merit in writing in a non-standard structure.
Take Dracula for example. While there is a linear timeline, it is written and structured as a collection of journals, newspaper clippings, and other writings as opposed to a straight-forward narrative. Likewise, a shifting, out-of-order timeline can turn conceptions of how the characters and plot develop on its head. What about the book-within-a-book concept, utilizing in-universe fiction to inform us about the actual world and plot of the story?
Even something as simple as alternating viewpoints is a deviation from the standard narrative structure, especially if you use an approach of conflicting unreliable narrators. Take inspiration from such famous narratives as the films Rashomon and The Usual Suspects. There’s a wealth of options to explore in creating both a unique story AND a unique way to tell that story!
Think about what would work best for the plot, the characters, and the themes you want to explore in your works. Never limit yourself to traditional narratives, but also never forget that they exist! Sometimes, the old ways ARE the best!
Until next time, good reading, good writing, and good luck!