While layout it uncertain until it's done, the book is looking like 46-48 interior pages in length.
It will have a Credits page, Table of Contents, Main Text, Index, Backer Thank-You page, and two-page Quick Reference Guide.
The interior is full-color throughout. There is a background image, at least 22 pieces of full-color art, and while the text is mostly black, judicious use of color for headings, tables, and equations enhances the look and usability of the book.
There will also be internal hyperlinks for easy navigation, and the document will have (at least) three layers - Background, Art, and Text, that can be toggled for fast or low-toner-use printing.