This genre has always intrigued from the time I read 'And Than There Were None'. I thought it was a great mystery novel, but I've read other books from the mystery shelves that aren't so great. Some plot lines are too complex and you really don't care about the who dunnit as you get closer to the end. I've tried writing a couple of mystery short stories, but I can't do it properly. Either the stories I write are too obvious. Or so complex the person I've had read them is left scratching their head. Any pointers other than study more novels?