I bought this planning to build such an instrument. After reading it cover to cover I feel that the instrument could be constructed by someone with reasonable technical skill without too much pain. I'm planning on modifying some of the design by updating the data acquisition hardware and writing my own control/signal processing code, but I'm sure that the code provided works well also. I may also add a couple more panel indicators to give students a better picture of what the instrument is doing each step of the way.
All the parts lists were very complete, even with prices at the time of publication (2008) and part numbers. The first chapter on how the instrument works is understandable on a basic college physics level while more advanced readers are sent to specialized papers and books. Using a higher resolution ADC I'm sure interesting experiments could be done beyond just a simple magnetometer. It seems the unit is rather heavy, but maybe experimentation will let the advanced builder construct another prototype. Congratulations on a well written document to the Hollos brothers.