Adrian Mastronardi has released a book called Half a Second; it is a detailed look into the XZ backdoor attempt of 2024. The book is freely available under a (non-free) noncommercial, no-derivatives CC license. Half a Second tells that story as one continuous narrative: the burned-out volunteer who maintained the code alone and was patiently, expertly manipulated into giving it up; the engineer whose half-second of curiosity caught the attack through a chain of luck and hard-won instinct; and the operator who built it, who has never been identified and, this book argues, may never be.