Hi Paul,
It is a bit tricky to tell as the final version is a combination of the two on line documents. “Analysis and interpretation of Astronomical spectra” and “Practical Aspects of Astronomical Spectroscopy” Also the on line copies I have are probably not the last versions that Richard published (mine are v8.6 and v2.0 respectively). Perhaps Marc has a better idea of what has been added/changed significantly. Alternatively a comparison of the list of contents might show up any obvious differences.
Cheers
Robin