It does indeed work. I can confirm after respeccing my archer and losing barrage that there is no way in game to get this book back. After save-scumming the vendors in the homestead, cyseal and luciell (sp?) forrest and none of them ever had this book even after refreshing their inventories over 100 times each. So I found the lstools link on the steam forums (listed below) to edit my saved game and was able to successfully restore this skill! So happy now. Note that I also restored my respecced pyro mage's burning blaze spell that I also couldn't get any other way. I even threw away 10k gold as a role-playing recompense to make my conscience feel better for hacking the game and pretended that the skill books were 5k each. In summary, you CAN get this skill back if you're willing to spend 20 minutes to follow the below link, pretty simple really, here is the link, see my post at the bottom with the relevant key name and values to use:
http://steamcommunity.com/app/230230/discussions/0/45350791694065464/Hope this helps:
Koth.
