Smoke and Iron, by Rachel Caine

Jess Brightwell is back in the belly of the beast, facing off with the Archivist of the Great Library in Alexandria, but this time he is impersonating his twin, Brendan. It is a desperate last ditch effort to combat the tyranny, enacted behind the backs of half his friends and allies. Even if he pulls it off they may never forgive him, which is problematic as he will need all their strengths to pull it off. Teacher Wolfe, general Santi, obscurist Morgan, engineer Thomas and soldier Glaine all have something to contribute, but it is the scholar Khalila who emerges as their true leader as she realises they need a plan for what comes after, should they miraculously succeed in their rebellion. This fourth book of the Great Library series was supposed to be the final one but, like Khalila, Rachel Caine clearly saw another story in its aftermath and there will be a fifth. This is a good thing as a gripping tale has invested us in discovering the future of the Great Library, if only to see if our intrepid eight can survive yet again. Each of the tight team of scholars and soldiers has suffered enormous loss in their quest to free the Great Library. With enemies gathering around the weakened institution how will they and it recover?