Cherie Priest - Fiddlehead (Clockwork Century #5, epub)[j_ray]

Young ex-slave Gideon Bardsley is a brilliant inventor, but the job is
less glamorous than one might think, especially since the assassination
attempts started. Worse yet, they're trying to destroy his greatest
achievement: a calculating engine called Fiddlehead, which provides
undeniable proof of something awful enough to destroy the world. Both
man and machine are at risk from forces conspiring to keep the Civil War
going and the money flowing.

Bardsley has no choice but to ask his patron, former president Abraham
Lincoln, for help. Lincoln retired from leading the country after an
attempt on his life, but is quite interested in Bardsley's immense
data-processing capacities, confident that if people have the facts,
they'll see reason and urge the government to end the war. Lincoln must
keep Bardsley safe until he can finish his research, so he calls on his
old private security staff to protect Gideon and his data.

Maria "Belle" Boyd was a retired Confederate spy, until she got a
life-changing job offer from the Pinkerton Detective Agency. Pinkerton
respects her work, despite reservations about her lingering Southern
loyalties. But it's precisely those loyalties that let her go into
Confederate territory to figure out who might be targeting Bardsley.
Maria is a good detective, but with spies from both camps gunning for
her, can even the notorious Belle Boyd hold the greedy warhawks at bay?

Another rollicking alternate history from Cherie Priest--Fiddlehead is
the fifth book in the Clockwork Century steampunk series that started
with Boneshaker.

Title: Fiddlehead
Series: The Clockwork Century
Author: Cherie Priest
Published: November 12, 2013, by Tor
Language: English
Genre: Steampunk
ISBN-10: 0765334070
ISBN-13: 978-0765334077
Length: 368 pages