A truly interesting and great topic with lots of maddening contradictions!

'Voices of Liberation' by Zeilig and JC Kongo is a good modern book containing a brief background history of post-colonial Haute Volta (as it was) and the context of Sankara's rise to power as well as transcripts of interviews and addresses he did

'A Certain Amount of Madness' edited by Amber Murray is a brilliant collection of 20 or so academic essays on sankara on various aspects and of various opinions of his time in power including the effects of his legacy in the Campaore era leading up the 2014 uprisings

Obviously straight translated transcripts of his speeches like 'Sankara Speaks' and 'Women's Liberation' make good sources for the actions and convictions of the man

I've also found a couple of useful pieces online on Jstor, namely 'Ideology and Praxis...' by Guy Martin which was published just months before Sankara's assasination and examines his grassroots support and also 'Charisma and Power...' by Elliot P Skinner who was the US ambassador to HV in the 70s and early 80s and he offers a unique and objective look at Sankara and his eventual downfall

And though I don't own it I know Ernest Harsch (who has done a biography of Sankara called 'An African Revoltionary') has also written a book on Burkina Faso called 'Power Protest and Revolution'

Not sure if this helps, I haven't got much on the wider history of BF (apart from Harsch )unfortunately as due to the nature of the topic there is little accessible material, let alone in English but as interest in Sankara and his legacy is growing in Europe and the US (dk where you're from) more and more critical and academic analysis is coming to prominence with VoL and CAOM that I mentioned above both being published in the last few years