In A Grammar of Murui (Bue), Katarzyna Wojtylak provides the first complete description of Murui, an endangered Witotoan language, spoken by the Murui-Muina (Witoto) people from Colombia and Peru. The grammar is written from a functional and typological perspective, using natural language data gathered during several fieldtrips to the Caquetá-Putumayo region between 2013 and 2017. The many remarkable characteristics of Murui include a complex system of classifiers, differential subject and object marking, person-marking verb morphology, evidential and epistemic marking, head-tail linkage, and a system of numerals, including the fraternal (brother-based) forms for ‘three’ and ‘four’. The grammar represents an important contribution to the study of Witotoan languages, linguistic typology of Northwest Amazonia, and language contact in the area.