He was the author of several books of mathematics, astronomy, and astrology. Among the last is a prognostication for 1594. However, Petrus Ryff is best remembered for continuing and publishing the Basler Chronicles his granduncle Fridolin Ryff maintained between 1514 and 1541. After Fridolin died the chronicles were bequeathed to his daughter Magdalena, who passed them on to Petrus Ryff. He continued the chronicles from 1543–1585, and in 1585 he published the chronicles. The Basler Chroniken were edited and re-published in 1872 by the Historische und Antiquarische Gesellschaft zu Basel. They provide an invaluable source of information about the history of Basel, and that part of Europe in the 16th century.
Historiam Basiliensem, quam patruus ejus Fridolinus Ryff, senator ac scholarcha, a primordiis urbis inceptam & ad sue usque tempora protactum reliquit, ab a. 1514 ad vitae suae terminum continuatit, qua vero hactenus non fuit edita. Basel: 1585.
Sphaera mundi : hoc est, Elementa cosmographiae, legibus logicis, in usum Acad. Basiliensis, Basel: 1593. OCLC258505324
Quaestiones geometricae, in Euclidis et P. Rami - Quibus geodesiam adjecimus per usum radii geometrici, Frankfurt: 1600. OCLC60916808
Compendium arithmeticae Vrstisii, Oxford: 1627
Editio Altera, cui accessit Commentatio Optica, sive brevis Tractatio de Perspectiva Communi, Oxford: 1665