These are past suggestions from MR readers, pulled from the comments, endorsed by me only on a stochastic basis:
Michela Wrong, Eritrea
Rwanda: something Prunier, probably Rwanda Crisis though it stops in 1996
Uganda: Season of Thomas Tebo, though it’s fiction (is that disqualifying?)
Eastern Congo: Jason Stearns Dancing with Monsters (like China, the country is too big for one book)
The Government of Ethiopia – Margery Perham’s Ethiopian answer to Ruth Benedict’s Japanese The Sword and the Chrysanthemum.
Ethiopia: – Wax and Gold by Donald Levine – Understanding Contemporary Ethiopia (edited by E. Ficquet & G. Prunier
Pre-colonial Africa: The Scramble for Africa
For DRCongo, I recommend The Congo: From Leopold to Kabila by Georges Nzongola-Ntalaja. It does a great job of distinguishing between the dizzying array of political factions in Congolese history. It’s shortcomings are in culture and economics. Not a lot to choose from with DRC unfortunately!
From Genocide to Continental War, by Gérard Prunier
In the Footsteps of Mr. Kurtz was excellent, as was King Leopold’s ghost on the DRC.
Zimbabwe – The Struggle Continues: 50 Years of Tyranny in Zimbabwe by David Coltart
Great Lakes region: this was actually good https://www.amazon.com/Great-Lakes-Africa-Thousand-History/dp/1890951358/
On Australia: Robert Hughes’ “The Fatal Shore: The Epic of Australia’s Founding”
On Hong Kong: Gordon Mathews’ “Ghetto at the Center of the World: Chungking Mansions, Hong Kong”
Tyler mentioned Joshua Jelly-Schapiro’s book on the Caribbean for the region, so how about Paul Theroux’s book about the South Pacific, “The Happy Isles of Oceania”?
And if Boston were a country: J. Anthony Lukas’ “Common Ground” J. Anthony Lukas
What about outer space? Best book on Mars? The moon?