- Inscription skills and Talismans will
not directly improve the properties on your spellbook. They just help to succeed more often when attempting to craft the spellbook, thus resulting in less scrolls wasted, faster spellbook production and less money spent per spellbook.
- Exceptional quality will
not improve the properties on your spellbook. It's just used to apply the maker's mark on the book.
- Magery skill
will improve the properties on your spellbook. At 100 Magery, in principle you can already craft spellbooks with maximum number of properties and maximum intensities. However, raising Magery to 110 and better to 120 will improve your chances to get more than one property on the spellbook. With more properties per spellbook, your chances to get the "good" properties on a book (like Slayers) are improved.
I've heard all sorts of urban legends about Inscription, for example that raising your Magery as high as possible above 120 with jewels improves your books, but they have no developer confirmation - anyway try whatever makes you feel lucky
In summary:
- Get 100 Inscription and a +30% Inscription talisman to waste as few scrolls as possible when scribing
- Get 120 Magery for best quality spellbooks