How do I keep my story bible consistent across books?

A story bible fails in a predictable way. Book one is written from memory and the bible is written afterward, so it captures what you remember rather than what is on the page. By book two the bible has three versions: the document, your notes in the margins, and the manuscript itself. By book three a character who lost her left eye in chapter four is wincing with her right, and a city that fell in the first book has a thriving market in the second.

The problem is not discipline. It is that a document made of prose cannot be checked. You can only reread it, and rereading forty thousand words of notes before every chapter does not happen.

One record per thing. Every character, place, faction, artifact, and event gets exactly one entry. If a fact lives in two places it will eventually disagree with itself.

Facts separate from prose. Under each entry, keep a short list of hard facts in a fixed shape: eye color, birth year, allegiance, date of death. Prose is for texture. The fact list is what you check against.

Every mention links back. When the manuscript or another entry names a thing, the name should resolve to the one record. This is what a wiki does that a Word document cannot.

Check before you continue. After each chapter, compare what you wrote against the fact lists for everything that appeared in it. This is the step everyone skips, because by hand it is slow.

The facts that break most often across books are the boring ones: ages and birth years, physical details, who knows what and when they learned it, distances and travel times, the order of events, and which named things are alive, standing, or already destroyed. Themes and character arcs rarely contradict themselves. Dates and eye colors do.