Ash & Quill, by Rachel Caine

Out of the frying pan and into the fire describes the continuing saga of the group of scholars in rebellion against the tyranny of the Great Library. They have fetched up in the Burner HQ of Philadelphia, which has been under siege by the Library for a century, but find that the enemies of their enemy are not necessarily their friends. Escape comes at an enormous cost to all and the next fire awaits in the form of Jess Brightwell’s family of ruthless book smugglers, who will help the rebels but at a very high price. Jess must think three steps ahead and even betray some of his friends to ensure the rebellion continues with some chance of success. But will any of them survive? And if they do can they forgive each other for what they have had to do to get there?