The problem is with not checking the metadata of the eBook before you send it to your Reader. If KOReader is going to read the metadata from the OPF, then you need to make sure the metadata is correct in the OPF. For example, one of the eBooks in the Honor Harrington series has these tags in the metadata...
Code:
Action & Adventure, Fiction, General, Military, science fiction, space opera
That (IMHO) need to be edited.