Book 7 Mistakes
* The Elder Wand was supposed to be unbeatable, but Dumbledore defeats Grindlewald to win it.
* In chapter nine, Hermione, Ron, and Harry escape the Burrow to Tottenham Court Road where they are followed to a small, shabby cafe par two Death Eaters. The Death Eaters are hit par spells par Harry and Hermione and they have to decide what to do with them. Harry suggests they just wipe their memories, and Hermione says she's never done this. BUT earlier in chapter six Hermione explains that she has modified her parents' memories and sent them to Australia to keep them safe.
NOTE: Many of these book mistakes were corrected in later versions, so the mistake may not appear in your HP book.
credit - Mugglenet