"This book reviews in a nice and well-written way the most important topological methods in the study of boundary value problems associated to ordinary differential equations. It is understandable even with a minimal knowledge of functional analysis; as a consequence, it is useful for many readers, starting from Master's degree students and up to experienced researchers, who will appreciate this thorough and self- contained description of the basic concepts in this field." (Anna Capietto, zbMATH 1319.34001, 2015)