It took me awhile to get through this one. It felt like a gear catching and clicking, holding my interest for a few chapters and then dropping it again. It's one of those series where I liked book one significantly better than books two and three. SERIES SPOILERS AHEAD.
I think what it comes down to, is that without the chronofer that he lost in book one, Tobias had very little offensive options available to him. Not enough agency (especially since he and Mara had to care for a small child). Thus most of the super cool magic and action fell to the villainous assassin team of Lenna and Orzili and we didn't even see Tobias and Mara for whole swaths of the story. When we did, they mostly reacted or fruitlessly sought out a chronofer. I wish instead of breaking his chronofer, Tobias's had merely gone wonky/unreliable so that he still could use it a little. Or even that the devices made precise a natural magic possessed by the Walkers, Spanners, etc. (It also bothered me that if no inherent magic, how and why did devices come to be built anyway?) Anyway, just my two cents.