The most recent blowback season is all about Angola.

So another commenter has mentioned the most recent blowback season which is admittedly good but you should know they have a source list you can dig through if you prefer to read. I personally do

The African Liberation Reader is a three part compilation of writings from several liberation organizations in southern Africa. Angola is one of the countries focused on throughout. Prolewiki version: 1, 2, 3 (still being proofread but it’s basically readable and easily searchable) / PDFs: 1, 2, 3.

Search these for Angola, MPLA, UNITA, FNLA, Agostinho Neto, etc. It’s also worthwhile to read some of the works in the compilation which aren’t specifically focused on Angola, as they can still provide good context for liberation in southern Africa and on the countries colonized by Portugal. The editors’ introductions to the chapters provide some overviews. Volume 1 starts with a chapter, “The Portuguese Empire”, the articles in that chapter would probably be a good starting point. Note, I am still learning about this and reading through this compilation myself so take my suggestions with a grain of salt.

There are also some chapters on Angola in Dirty Work: The CIA in Africa.