You may be asking yourself 'What is a polycystine radiolarian and do I care about paleobiology?' Well, first, you probably do know what polycystines are but don't realize it. They are the major constituents of the phylum Radiolaria in recent classifications. In ISOP's latest scheme (Adl et al. 2019), the class Polycystinea is composed of the orders Spumellaria and Nassellaria. They are remarkably species-rich groups of radiolarians in terms of both living and fossil forms distributed in literally hundreds of genera. Their siliceous skeletons, or shells, are iconic of the beauty of protists, made famous for example, by Haeckel in his Kunstformen der Natur (e.g., Fig 1). Second, despite the title, paleobiology is actually not the main focus of the book; it could have been more accurately titled 'The Biology, Ecology, Evolution of Radiolarians Living and Fossil'. The only inaccuracy of such a title is that some might have expected the book to include Acantharians and Phaeodarians. Acantharia are not treated and Phaeodarians, alas, are no longer considered to belong within the Radiolaria. However, the polycystines alone are a large enough subject to easily fill this substantial volume.