Subtitled 'a programmer's companion, this is a slice of nostalgia from a time when I wasn't actually using computers. Covering the (ahem) golden age of CP/M, it's a bit of an insight into the pre-MSDOS days and MSDOS itself, given how it builds on CP/M. It's interesting to see the future plans of CP/M that never happened. It's also quite scary to see a time when you could copy an executable by running it, quitting, and then dumping your memory image to disk afterwards. Freaky.
What's quite impressive is how poor this book is. Three authors, three distinct styles, and often the same thing repeated three times. Chapters are badly ordered, badly laid out, and there are numerous spelling mistakes. Much of the information feels like it was copied out of other documentation (in fact, the last chapter is, explicitly). There is a wealth of information here, on diverse topics, from the basic command processor through using text editors, compiler error messages for various languages, and how to do low-level system calls. It's an impressive feat to put them all in one book, and pretty shocking how badly they've done it and still been able to get it published.