Where can I see a timeline of everything that happened in my book or series?

Open the book, click "Codex" above the chapter list, and choose the Timeline tab. It lists every finished chapter in order with a short recap of what happened in it — and if the book belongs to a series, it shows all the volumes in order, so you can review the whole saga at a glance. Recaps are created automatically while fiction chapters are being written (from v1.7.0 on), so books generated with older versions show their chapter titles until new chapters are written or regenerated.