The papers provide an incomplete overview of Thordarson's life, touching on his library, his inventions, and his business. The collection has little about Thordarson's accomplishments as an inventor and as a collector of rare books. Nor does the collection document Thordarson's association with the men of power and renown whose friendship he cultivated. The papers are arranged into eight series: CORRESPONDENCE, ROCK ISLAND, THORDARSON LIBRARY, INVENTIONS, BUSINESS AND FINANCIAL RECORDS, EXHIBITIONS, PRINTED ARTICLES, and PERSONAL.

The CORRESPONDENCE series is arranged by subject and then chronologically. The General Correspondence is almost exclusively related to Thordarson's business, but it is not possible from this file to get a picture of the significant developments in his business career. In one brief letter from Edward Bennett, a University of Wisconsin professor of electrical engineering in the 1930s, it is noted that Thordarson's company was taken over by the Burgess Company in the 1930s, however other letters concerning the business are less informative.

Material on ROCK ISLAND is fragmentary. The Correspondence consists almost exclusively of letters to and from Thordarson relating to routine maintenance of the island. Filed here is the only evidence in the collection of Thordarson's close friendship with Chicago Mayor William “Big Bill” Thompson: a copy of a letter from Thordarson to Thompson dated 5 December 1924 in which Thordarson agreed to construct a cabin on Rock Island for Thompson's lifetime use. The Construction - Correspondence and Orders file concerning construction of the early log buildings and the later Icelandic-style stone buildings, is not extensive or substantive.

Documents pertaining to the THORDARSON LIBRARY are likewise unrevealing. The Bibliographies in the collection may be a list of Thordarson's books. The Correspondence is primarily to and from people interested in visiting the library or in selling privately-owned books to Thordarson. There is little that documents Thordarson's important association with the Chicago book dealer Walter Hill or his friend J. Christian Bay, librarian of the John Crerar Library. Much of the material in this section consists of copies of drawings and poems in Old English from the library's collections.

The INVENTIONS series is in the form of patents and patent applications, drawings and blueprints (usually unidentified), and notebooks in Thordarson's own hand about his experiments. The data in the notebooks is sketchy.

There is no orderly set of records documenting Thordarson's personal business and financial affairs or those of the Thordarson Electric Manufacturing Company. The Bankbooks of the BUSINESS AND FINANCIAL RECORDS series give only figures and do not indicate the company's sources of income or expenses. Payroll records are fragmentary lists of workers and wages paid. The Company Reports are scanty. Flyers are leaflets and information or instruction sheets; these concern company products, as do the Catalogues.

Material relating to Thordarson's participation in two major EXHIBITIONS does not reveal much about the electrical inventions he exhibited there.

There is very little documentation of a personal nature in the collection. The PERSONAL series offers virtually no information about Thordarson's wife, Juliana Fridriksdottir (Gilson) Thordarson or of their two sons, Dewey and Trygve. However, there are a number of letters from Thordarson's brothers, sisters, nieces, and nephews.