In the detail of feat Draconic Arcane Grace there's a note:
Note: This feat requires the use of the new spellbooks, so if they are disabled this feat will not work. If you are a bard or sorcerer and not already using the new spellbooks, you will be converted to them.
So it seems that a sorcerer can use the old spellbook system... then I tried this, and found that a pure sorcerer can, but when gained a prestige class such as Archmage the old spellbook is forbidden. Is there a switch or so that can make it available?
Thanks!