London Falling: Paul Cornell

'An irresistible blend of guns, gangsters, cops and monsters' Ben Aaronovitch
The dark is rising . . . Detective Inspector James Quill is about to complete the drugs bust of his career. Then his prize suspect Rob Toshack is murdered in custody. Furious, Quill pursues the investigation, co-opting intelligence analyst Lisa Ross and undercover cops Costain and Sefton. But nothing about Toshack's murder is normal.
Toshack had struck a bargain with a vindictive entity, whose occult powers kept Toshack one step ahead of the law - until his luck ran out. Now, the team must find a 'suspect' who can bend space and time and alter memory itself. And they will kill again.
As the group starts to see London's sinister magic for themselves, they have two choices: panic or use their new abilities. Then they must hunt a terrifying supernatural force the only way they know how: using police methods, equipment and tactics. But they must all learn the rules of this new game - and quickly. More than their lives will depend on it.
'He's gone and written a novel too! I suspect it will be just as good as everything else he's written, and that's not fair at all' George R R Martin