Foster was an avid collector of books and bookplates. The bookplates make up the first series of the collection. He collected many copies of "Uncle Tom's Cabin" and also kept scrapbooks on Harriet Beecher Stowe. These scrapbooks make up the second series in this collection. Foster was also a writer and his manuscripts make up series three of this collection. Foster collected many volumes on Shakespeare and believed that Edward de Vere wrote the plays attributed to Shakespeare. His manuscript for Skakespeare, Man of Mystery is a part of this collection. Clippings and other items make up the last series, Miscellaneous.