Absolutely loved this book! Lots of details about the development of the game but more importantly the how and why of optimization decisions which only made sense for the platform it was developed on or to get around limitations of the time. Comments from Carmack and others years later on things they wince at as being naive or things they wince at as being bad things to do with later computers also was well done. Anyone into retrocomputing down to the nitty gritty level will enjoy this book. If you haven't read Masters of Doom yet you should. It is a great companion to the book which covers lots of the time before and after the period addressed here but in a much broader level of detail and therefore with less depth on the algorithms and code itself.