Chapters, or acts, in Inscryption are not clearly defined — when you transition from act to act, there is no title text or indication that you have changed chapters. Instead, players are expected to intuit it from the radical environment changes. However, once you complete the game, a chapter select unlocks, allowing you to replay whichever chapter you choose instantly.
According to the chapter select, there are 5 chapters — consisting of the Tutorial, Leshy’s Cabin, Inscryption, Botopia, and the Credits. If you remove the Tutorial and Credits, you have a 3-act structure consisting of the Cabin, Inscryption proper, and Botopia. This doesn’t include the videos of Luke Carder’s discovery of Inscryption, as those seem to act as intermissions between each chapter.
Most players will find Leshy’s Cabin and Botopia to be the longest chapters, likely due to the enhanced animations taking a little longer to complete when compared to Chapter 2’s pixelated art and animations. That said, Chapter 2 arguably has the most depth with card strategies, allowing players to utilize the Beastly pantheon and use Technology, Death, and Magic pantheons. Furthermore, Chapter 2’s wide range of strategies make for some fairly annoying boss fights — unless you abuse Bone Heap, that is.