The effect of Silk Touch overrides that of Auto Smelting. It would be better if these two are mutually exclusive so the player doesn't accidentally waste an enchanted book.

I just tested with a pickaxe that had only Auto Smelting on it and it still had no effect at all. I checked the log but didn't find any useful information.
latest.log

Has been changed, you shouldn't be able to use silk touch with it now