This is Liddel's copy of the second edition of De revolutionibus. Although he owned a copy of the first edition, it was in this second edition that Liddel annotated most extensively, with original notes and diagrams of his own and those of the celebrated astronomer, Paul Wittich, who studied with Liddel in Wrocław.
This particular copy of De revolutionibus is famous however because it contains a complete manuscript copy of an earlier work by Copernicus, the Commentariolus or ‘little commentary.’ This is a earlier version of the Copernican theory that the sun was at the centre of the cosmos which had been circulated amongst astronomers for many years before the final publication of De revolutionibus. Only three copies of this manuscript are known to survive today, the original by Copernicus being lost. It has been suggested that the Commentariolus was passed from Georg Rheticus to Thaddeus Hajek to Tycho Brahe to Heinrich Brucaeus and finally to Liddel who made this copy, evidence of the links in the network of astronomers and mathematicians in late sixteenth-century Europe. It is written on sheets interleaved throughout the printed book, each sheet at the relevant printed section.