I believe I purchased Carole Cummings‘ Blue on Black from the publisher when it was on special, last year.
Description from Goodreads:
Kimolijah Adani—Class 2 gridTech, beloved brother, most promising student the Academy’s ever had the privilege of calling their own, genius mechanical gridstream engineer, brilliantly pioneering inventor… and dead man. But that’s what happens when a whiz kid messes with dynamic crystals and, apparently, comes to the attention of Baron Petra Stanslo. Killed for his revolutionary designs, Kimolijah Adani had been set to change the world with his impossible train that runs on nothing more than gridstream locked in a crystal. Technically it shouldn’t even be possible, but there is no doubt it works.
Bas is convinced the notoriously covetous and corrupt Stanslo had something to do with Kimolijah Adani’s tragic and suspicious end. A Directorate Tracker, Bas has finally managed to catch the scent of Kimolijah Adani’s killer, and it leads right into Stanslo’s little desert barony. For almost three years, Bas has tried to find a way into Stanslo’s Bridge, and when he finally makes it, shock is too small a word for what—or, rather, whom—he finds there.
Review:
I think it really is possible to have too much of a good thing. I adored the characters here. I liked the snarky narrative style. There is some genuine humor that really colors Bas’ personality. I appreciated the interesting world and tech. I liked the slow burn in the relationship. (And it is slooooow, people. There are only two mild sex scenes in the whole 380 pages.) But the book is just too long. The middle drags on and on without anything that significantly moves the plot along happening. It’s just more of the angry, sarcastic interactions between the same characters, which are fun but not enough to keep a story afloat. I enjoyed the story. Don’t let me sound as if I didn’t, but I think it could have been improved on and I’d have enjoyed it even more.
Way back in 2014, I bought a copy of 
I picked up a copy of