Given that GRIM is a collection of short stories inspired by classic fairytales I don't think you need be familiar with those classics to read these. I for one have not read a ton of classic fairytales so my perspective on this does not compare them to whatever fairy tale might have inspired them. Some I recognized but most I really wasn't even trying to figure out what story might have inspired them. So I definitely went in hoping that the stories would speak for themselves and possibly turn me onto a few new authors - which I did find a few authors I will now check out. 
 I wasn't blown away by this collection overall but I do think I know a few young teen girls who would adore it. Half of what I read is young adult fiction so sometimes I can be a bit of a hit or miss when it comes to enjoyment. Ultimately, I had a few favorites but most others herein were just ok. Perhaps an avid lover of fairy tales might appreciate it more for being able to recognize which story had inspired it?? I'm always up for reading short fiction collections because I have never walked away from one where I haven't immensely enjoyed one of the stories. 
 Keep in mind these are a mix of sci-fi and fantasy toned stories. I personally like both genres, though I've always been an avid lover of fantasy stories in this collection I seemed to lean towards a few of the sci-fi ones!