The Principle of Mutual Trust in EU Criminal Law is very timely piece of scholarship, one which adopts a novel approach vis-à-vis the understanding of trust in EU criminal law. While most previous work on mutual trust in EU criminal law has concentrated on EU case law, Willems gives us a theoretical baseline for how to understand trust, one which includes both interdisciplinary and comparative perspectives that are both new, legally sound as well as entertaining to read. It is a very well-researched and well-written book, which will be of use and of great interest to both academics, LLM students as well as to policy makers.