This volume brings together fifteen seminal essays by Thom Mertens, a professor at the Ruusbroec Institute (Ruusbroecgenootschap) at Antwerp University since 1985, and a pioneer in the study of the late medieval spiritual literature of the Low Countries, a field that had previously been neglected in favour of the study of belle lettres. This volume is therefore also a celebration of the paradigm shift that Mertens led, as he demonstrated that most of the late medieval texts produced in the Low Countries actually qualify as spiritual literature, and that these understudied literary works are of prime importance within late medieval textual culture. Of the essays gathered here, nine have been translated into English for the first time, while six have been re-edited, forming a collection that bears witness to the importance of Dutch literature as a broader part of the vernacular literatures of Western Europe, and of the societies that gave rise to these works. It is in large part thanks to Mertens' efforts that serious scholarly engagement with these spiritual texts, their characteristics, and their function has become a field of research in its own right that continues to flourish.