Drawing on existing work on popularizations, this investigation of book-length scholarly essays by practicing scientists across three disciplines reveals a hybrid genre that is neither popularization nor research report. The study utilizes both textual analysis and personal commentary from the writer-researchers to achieve a three-way comparison between the popularization, research article, and the book-length scholarly essay that clarifies how these essays contribute to the authors' academic agendas. Writing for both a general audience and a jury of their peers, these academics employ an argumentative generic structure. Such argumentation develops a rhetoric of rational inquiry, where understanding how answers to perplexing problems are arrived at is just as important as the answers themselves. This genre also suggests the possible resurfacing of the essayist tradition in the sciences, as these practicing researchers engage with wider audiences in theoretical and philosophical speculation.