"French, Language of Instruction or Language to Teach" is an academic book that addresses the question of which educational model promotes the best language skills in an official language when this language is not the mother tongue of the learners. The study focuses on the multilingual context of Africa in the 21st century and employs various theories of language learning along with four specific case studies. The author, E. J. T. Bos, argues that a model based on the first language that leads to additive bilingualism yields the most effective results in terms of language proficiency. The analyzed case studies come from Sweden, Cameroon, Burkina Faso, and Niger, providing valuable insights into the challenges and opportunities of language learning in multilingual societies.