Single Digits by Marc Chamberland
6 out of 10118 prosaic vignettes covering various topics in modern mathematics. Some of the material was refresher from my days in the classroom, but concepts such as
Marden's Theorem ~ The Wendt Determinant ~ Long Primes ~ Strassen Multiplication ~ Singmaster's Conjecture ~ Non-Associative Octonions ~ ...
were novel to me.