It's no secret that I'm not a big fan of Simon. Although I must say he was less irritating than usual, at least in the first few stories, and I did find his whole ordeal and dilema interesting. I would still have preferred for another character to frame the short stories, but well. 
 Favourite story was obviously Born to Endless Night, even though it got quite fanficcy at times (like a lot of the stories). Also in the top 3, The Whitechapel Fiend and Nothing but Shadows. 
 It fills the gaps quite nicely between The Mortal Instruments (and even The Infernal Devices) and Lady Midnight, and it's nice to see how some characters got on after the end of their story. Is it worth a read just for that? Probably. 
 Other than that, though, Cassandra Clare's writing still has its flaws (even in English, there's only so many times you can use someone's name in the same paragraph without it sounding awkward), but she does have compelling characters and some of the storylines can be nice. So if you're a fan, why not?