FlexiBook

A mod for pack authors and mod developers.

Features: multilingual support, insert images, custom fonts, custom text colors, clickable links, auto re-layout when switching languages, automatic pagination, custom book backgrounds, search and locate image keywords, and caching layout results to boost performance.

Includes an editor that can be launched directly or packaged as an Electron app.

You can register new books using pure texture packs, and the editor lets you export or import texture packs for editing.