Quote Originally Posted by ForteXX View Post
http://i.imgur.com/HaTAo4p.png

Image (from Veil of Wiyu Atma thread), showing that stats are -not- customizable (all finished weapons will currently be the same, as each book gives specific stats to the weapon; note the 9 total obtainable books, rather than a "pick 9 books"). Only part that is currently 'customizable' is what the stats will be until you get the end weapon.
Not yet anyway, they did say they would be customizable in a later patch.