Sorry, but my inclination is delete here. This feels entirely speculative to me-- all Hermione said was that she "read all about them," not that that she read a book about them. It was stated that she got a number of books for background reading, and any of them could have covered jinxes as part of its subject matter, possibly one that we already have listed. ProfessorTofty (talk) 23:05, March 22, 2013 (UTC)

I just figured it was better to be safe than sorry, that it was better to have everything covered than possibly missing something. Feel free to delete it if you want :) --"It is real, isn't it?" "It's real for us." 23:09, March 22, 2013 (UTC)
I'm deleting it. Sorry, but while there is a case for inclusionism in some things, the existence of this book is entirely speculation. ProfessorTofty (talk) 02:35, March 24, 2013 (UTC)