A Long Spoon (Johannes Cabal, #4.5)

You may have heard of Johannes Cabal; he is a necromancer and a little infamous. He is also very sensitive to attempts on his life. When a murder of crows tries to... well, murder him, and the contents of his bath are transmuted into hot nitric acid, he suspects someone may mean him harm. The trail leads to one of the less travelled parts of Hell itself, and there Cabal will need a guide.

As Dante had his Virgil, so Cabal employs the services of a devil who is a monster, a predator, and -- most alien of all to Cabal -- a woman. The devil Zarenyia and he delve deep into Hell, even into Satan's greatest mistake, to confront challenges quite outside the ken of any mortal. But one should always use a long spoon when supping with a devil, and Cabal soon realises the unthinkable, a horror beyond his experience. He is actually beginning to like her.