Activist Angolan rapper Luaty Beirao and 16 other dissidents have been sentenced to prison for planning to overthrow president Jose Eduardo dos Santos at a book club meeting.

Beirao and the group were arrested in late June after participating in a book club discussion of Gene Sharp’s 1993 book on nonviolent resistance, From Dictatorship to Democracy: A Conceptual Framework for Liberation. Angolans have called the trial a farce and international human rights groups described the verdict handed down by a court in Luanda as ”outrageous.”

More optimistic observers see the trial of the “15+2”—15 activists arrested and jailed since June, plus two other accused who were not detained—as a tipping point for public outcry. Oil-rich Angola has grown to become the continent’s third largest economy since the end of its civil war in 2002, but citizens are increasingly angry about government corruption, repression, and violence. Demonstrations against the group’s arrest have continued despite police crackdowns on protests.

Dos Santos, Africa’s longest serving leader after Equatorial Guinea’s Teodoro Obiang, said this month that he would leave “active politics” in 2018 after the country’s next election is in 2017. Dos Santos has held his position since 1979. Skeptics have questioned why the 73-year old did not volunteer to step down before the election and whether he would quit as head of the ruling party, the Popular Movement for the Liberation of Angola.

Beirao received five and a half years in prison. Domingos da Cruz, another activist who prosecutors deemed the the leader of the group, was given a sentence of eight years.