Sorcery, steampunk, Sherlock Holmes and an alternate world: first of a series from the author of Angel Town (2011, etc.).
Beneath Britain slumbers a huge, ancient, mighty dragon; if it ever wakes up, its fire will destroy the world. In Londinium, Queen Victrix, the current incarnation of the goddess Britannia, commissions Emma Bannon, Sorceress Prime, to protect Archibald Clare, a failed and now unregistered mentath—due to a mistake, he served time in prison for reasons only hinted at—capable of extraordinary feats of deduction. Mentaths, for whom data manipulation is a compulsive need rather than a means to an end, have more in common with Frank Herbert's human-computer Mentats than legendary fictional detectives, however. Bannon has formidable skills, although how magic works is far from clear. She mistrusts Clare and won't give him the data he needs, while he, naturally, is extremely well-informed, except, oddly, about sorcery, and considers her illogical. Mikal, Bannon’s lone Shield, or protector (he kills nasty things that threaten her while she's preoccupied with sorcery), betrayed his previous employer, a treacherous sorcerer; secretly, he's a shape-shifting serpent—and her lover. Plot? Well, Saintcrow doles it out piecemeal, without giving Clare or the reader enough clues to add up, but somebody's killing registered mentaths and also sorcerers. The conspiracy possibly involves Cedric Grayson, Chancellor of the Exchequer. But to what end, and who's behind the conspiracy? Clearly not the clownish Grayson. Add to the mix a logic engine, dragons, gryphons, an Italian assassin, steam-powered clockhorses and the curious unavailability of hansom cabs.
Intriguing but messy; two of the chief ingredients would have sufficed, four is extreme overkill.