Create a new wizard character, go to Spells and Spellbooks tab. Manually add some 0 level spells to the spellbook. You can see the pages used increased by 1 for each 0 level spell added. After adding 4 spells, the wizards spellbook/blank shows 4/100 for pages/used.
Save character, close character, open character. Navigate to spells -> Spellbooks, and the spellbook shows 4/0 instead of 4/100. Can no longer add spells to the spellbook.
Fixed the linking of equipment to the saved spellbook on load. Characters already affected will be fixed when loaded in the new version.