There are two known errata as of 1-15-2025. * In the second half of the proof of Proposition 3.7.1, the various primes of x, y, z, a got a little convoluted. It's a good exercise to fix it. Thanks to Brenda Johnson of Union College for pointing this out. * In Historical Remark 12.1.7, there is now yet another Mersenne prime! It has well over forty million digits. See the GIMPS press release at https://www.mersenne.org/primes/?press=M136279841