Flex, by Ferrett Steinmetz
Lots of fun. It's like Breaking Bad goes Urban Fantasy. Magic is based on obsession. So if you are an obsessed cook, one day you can do cooking magic. A culinaromancer or gastromancer. And all the mancers can do one trick: they can create a drug called Flex that is their magic, devoid of special effects or foci, that everyday joes can take to do magic.
The downside is the side effects. If you break the laws of physics, either with your own magic or on Flex, you get unluck. A little magic stubs your toe, a lot fractures your hip, or kills you, or flattens your apartment building.
That last is why it is illegal. Anyway, I had lots of fun with this book.