Black, thin, warped, glossy cover stock instead of that super nice feeling matte white one, and much thinner nastier paper (despite being longer the book is much thinner).
I have in the past given copies of ‘Code’ to people who’ve seemed interested in learning about computer science/engineering with a ‘this book is so good!’ and upon reflection just now I’m ashamed to say I’ve stopped doing that because the book _feels_ like a cheaply made textbook rather than a nicely presented popular science book now.