Honestly much better impression of this on reread than when I rated it two years ago (I originally read it before Goodreads existed). This story has a lot of emotional heart and despite the functional issues with the plot (time travel just should never be included as an afterthought), it has some of my favorite moments of growth for Harry as a character. 
 (view spoiler)[ 
 It's really frustrating that it all falls apart because Lupin forgot to take his medicine, and just seems like a foolish oversight especially from a man who's been dealing with werewolfism since his childhood. But if you read through all the books and realize that the oversight was related to their hatred and relationship to Snape, it has more poetic meaning. (hide spoiler)]