[3] The first part discusses the earlier history of polyhedra, including the works of Pythagoras, Thales, Euclid, and Johannes Kepler, and the discovery by René Descartes of a polyhedral version of the Gauss–Bonnet theorem (later seen to be equivalent to Euler's formula).
[2][4] Euler's Gem is aimed at a general audience interested in mathematical topics, with biographical sketches and portraits of the mathematicians it discusses, many diagrams and visual reasoning in place of rigorous proofs, and only a few simple equations.
[9] However, the later parts of the book may be heavy going for amateurs, requiring at least an undergraduate-level understanding of calculus and differential geometry.
[4][10] Reviewer Dustin L. Jones suggests that teachers would find its examples, intuitive explanations, and historical background material useful in the classroom.
[7] Dustin Jones evaluates the book as "a unique blend of history and mathematics ... engaging and enjoyable",[11] and reviewer Bruce Roth calls it "well written and full of interesting ideas".
[6] Reviewer Janine Daems writes, "It was a pleasure reading this book, and I recommend it to everyone who is not afraid of mathematical arguments".