This Element describes for the first time the database of peer review reports at PLOS ONE, the largest scientific journal in the world, to which the authors had unique access. Specifically, this Element presents the background contexts and histories of peer review, the data-handling sensitivities of this type of research, the typical properties of reports in the journal to which the authors had access, a taxonomy of the reports, and their sentiment arcs. This unique work thereby yields a compelling and unprecedented set of insights into the evolving state of peer review in the twenty-first century, at a crucial political moment for the transformation of science. It also, though, presents a study in radicalism and the ways in which PLOS's vision for science can be said to have effected change in the ultra-conservative contemporary university. This title is also available as Open Access on Cambridge Core.