okay so that was Gideon the Ninth (slightly spoilery)
Overall I liked it.
My big issue is that after a fairly nice slow build, the story suddenly moves *very* rapidly from
1) revealing one character as incredibly powerful and manipulating things from behind the scenes for some time to
2) revealing that a different character is actually the main villain, with her own motivation, which doesn't feel especially clear, and this feels abrupt enough before
3) there's a hugely long climactic fight which keeps ramping up and having possible endings and by the time *that's* about 2/3 over I'd largely lost interest and kept pushing on for completion's sake.