The Tainted Cup by Robert Jackson Bennett

Regarding location - Google will may say that the Hugh is closed, but it is not. We will meet inside the food court and there will be sign holders on the table with the book cover on it.

From Good Reads:
In Daretana’s most opulent mansion, a high Imperial officer lies dead—killed, to all appearances, when a tree spontaneously erupted from his body. Even in this canton at the borders of the Empire, where contagions abound and the blood of the Leviathans works strange magical changes, it’s a death at once terrifying and impossible.

Called in to investigate this mystery is Ana Dolabra, an investigator whose reputation for brilliance is matched only by her eccentricities.

At her side is her new assistant, Dinios Kol. Din is an engraver, magically altered to possess a perfect memory. His job is to observe and report, and act as his superior’s eyes and ears--quite literally, in this case, as among Ana’s quirks are her insistence on wearing a blindfold at all times, and her refusal to step outside the walls of her home.

Din is most perplexed by Ana’s ravenous appetite for information and her mind’s frenzied leaps—not to mention her cheerful disregard for propriety and the apparent joy she takes in scandalizing her young counterpart. Yet as the case unfolds and Ana makes one startling deduction after the next, he finds it hard to deny that she is, indeed, the Empire’s greatest detective.

As the two close in on a mastermind and uncover a scheme that threatens the safety of the Empire itself, Din realizes he’s barely begun to assemble the puzzle that is Ana Dolabra—and wonders how long he’ll be able to keep his own secrets safe from her piercing intellect.

Featuring an unforgettable Holmes-and-Watson style pairing, a gloriously labyrinthine plot, and a haunting and wholly original fantasy world, The Tainted Cup brilliantly reinvents the classic mystery tale.