Two Serpents Rise
The Craft Sequence - Book #2
by Max Gladstone
This is called "The Craft Sequence", not "The Craft Series" for a reason. The series isn't structured as a normal series. Two Serpents Rise takes place in a different city with a completely new cast of characters from the first book -- but interestingly, the city and some of the major players were mentioned in the first book as kind of throwaway lines. This illustrates just how well thought-out this world is.
The story is once again focused around this contract-as-magic thing. The water supply of the city of Dresediel Lex, managed by Red King Consolidated (owned by a skeleton king!), has been corrupted, and it's up to Caleb to find out why. The Red King has a looot of creditors. With strong enough leverage, any of those creditors could cash in their chips -- souls in this case -- and absolutely destroy Dresediel Lex. In his investigations, Caleb runs across a mysterious woman, Mal, and falls for her. What's up with this chick? Is she good or bad? Does she know what's happening? Who knows? Is she even relevant to the main plot? Read to find out!
Seriously. Read it.