I would not worry too much about the programming side of this book. Most of the code is written in Pascal. Equally, I would view the hardware experiments as, at best, vaguely interesting. However the area that is of potential interest to a select band of people is the information on how to use the Centronic (parallel) port, the RS232 (serial port) and game ports as bi-directional data streams. While the use of RS232 ports from C and assembler is reasonably documented there has been a lack of detailed information on using the other two routes.
If you want to interface your computer to the outside world this book is worth reading. However you would be advised to read thoughtfully and act carefully. Perhaps you might prefer to recycle that ancient 386 based machine as a test bed rather than experiment with your all singing, all dancing Pentium II with AGP and USB connections.
Now who is going to write a book about interfacing through the card slots on your motherboard. Come to that, why not use the secondary IDE connector? I guess you could have some real fun rather than just limiting yourself to using a parallel printer port.