The mood was nothing like e.g. the Twoflower novels. But how can it? It deals with oppression and abuse of women, with war and death and identity and religion and perception and society and the struggle for power and a place in the world. It is probably the most serious in tone of all the Discworld novels I have read so far and it is again very wise.
I truly recommend this. You can read it as a stand alone even, you don’t really need to know who Vimes and Angua are. They only feature a little.