For enemies...

 

Surely it would make more sense to write Gilderoy Lockhearts 'text books' as they at least were supposed to have been written in the form of a story. It would be an interesting insight into some of the other people in the harry potter world and how they fought local monsters for lack of a better word.

 

And we all know Gilderoy would scream like a little girl and run away, lol.

 

Firstly we have knowledge that he stole the stories from other people that actually knew how to actually deal with the problems they came across. Secondly we know he was a best seller so his stories had to be fairly decent even if it would be impossible to reconcile the stories with the person once you know him

 

Best sellers within a small, secular community that probably had minimal fiction authors/interesting people who played to the press.