A spellbook is typically created one spell at a time, and is intended to allow pages to be rearranged, added, and removed. Students may use copper pages, but established professionals will typically use silver or, rarely, platinum for certain spells.
Some elder mages, late into their career, may have several platinum pages at the end of their spellbook.
Codex Nolie - A spellbook created and expanded-upon by Rimas Nolie. It was initially created in 532 GD as a single-page hand-written spell called Flamefinger, but eventually it grew beyond its bindings, requiring permanent locumancy enchantments on its covers, allowing the pages to expand indefinitely.