Slightly nitpicky?
Okay, then, MYK is the shared repository for all books linked at the account level.
Any specific book may or may not be compatible with a specific device, but MYK still lists them and lets you do account administrivia to it.
...
Maybe you can search the rootfs for the dictionary, mntroot rw and delete it. If you are jailbroken.
Bottom line -- the book has gotta be somewhere. The only question is, where, and how do you find it?