Yes, this is by Saki.

Have wanted to read this since mentions of it in introductions to his fiction, and then his biography included some quotes which whetted my appetite further. This was a whole book of Saki I hadn't read and could not find, a history of Russia with bits of snark. It was a 15 to 20 year search until I got my mitts on the book. In the end I picked up as a print on demand. No book could live up to that kind of build-up.

It's (as suspected) not brilliant, written before he'd found his spiritual home in short story land.

He seems to have researched his facts thoroughly then dumped the info randomly on the page, chronologically. I found it hard to tell the why of the sequence of events. There is some happy phrase making, for instance I enjoyed

Among the expedients for obtaining [money] which met with the approval of Christ's Viceregent, was the barter of indulgences, conducted in such wholesale manner that none but the very poor, who could not afford luxuries, were excluded from the attainment of eternal glory.

Most of his jokes came up when he was being blackly sardonic at the expense of the church militant. (He SO wanted to be gibbon when he grew up) Hence, I suppose, the pondorously augustan sentences and purple vocabulary

As the Polish eagles went winging homeward the land settled down, almost for the first time in the century, to a period of peace and security, and the figurative 'voice of the turtle' arose once more in the forests and fields of Moskovy.

It's told as a series of biographies of reigns, from grand princes to tsars. (The cut-off point where his history ends is 1619 when the Romanov dynasty became secure in power.) Saki is shocked, shocked! by Ivan the Terrible, in a tabloid editorial way that forces him to dwell on the despot's torture techniques. The early centuries, short on records, are eked out with a lot of geographical detail.

He had personal ways of transliterating russian words, some subvocalising might be needed to work out names at points. ( )