The author went through a great many original medieval documents (headaches guaranteed, reading that) pulling every instance of a proper noun that he found, and noting where it came from. He also noted, when it could be figured out, whether it was a place (marked "geogr" or "rio" or what applies) or a person. If the latter, he tried to figure out if it were the person's name (and which gender) or if it were "app.": a second name, a patronym (in some cases maybe a matronym), or some other form of "surname" (not yet family name). Two columns of this for over 400 pages, all alphabetically intersorted, which helps one figure out the second names.

My mother always told me that Portuguese was perfectly understandable if you speak Spanish, and as weak as mine is, I could still read this. There isn't a lot of text to deal with: it's all about the lists.

I can see this being used by re-enactors for a name the College of St. Gabriel will pass, but also by genealogists. The names are not "regularized," made to conform to some standard spelling, and may look more like the name you have in your records. Medieval records-keepers had no idea of regular orthography: the lists often note a source where the same person is refered to by two rather different spellings.

The work he did is heroic, and surely was a grind. I could wish, while he had the records and an idea of what area they were dealing with, he had attempted to tie modern names to the old geographic terms when possible: as it is, this castle or cathedral or mountain might be anywhere in Portugal, unless we go back and dig through the same records until we hit the same name--if those records still exist, a hundred years of accidents later.