The papers form two distinct sections. The first contains Monsell's correspondence, papers, illustrations and published works; the second comprises letters and papers of other family members. The first section include letters that Monsell wrote to his mother during the First World War, complete with sketches, drawings and annotated watercolours produced during and after the war. There are also significant quantities of Monsell's artwork and other illustrative material derived from his work as a children's book writer and illustrator, as well as musical scores, stage sets and costume designs for his musicals.
The second section includes nineteenth-century letters of Aubrey de Vere, with a file of his letters to an unidentified lady known only as 'Mrs Jackson'. Other items include an unpublished manuscript verse by the Anglo-Irish poet Percival Graves, together with other nineteenth-century family correspondence, family trees and two family histories, one by Monsell himself, the other by his grandmother, Eleanor Vere O'Brien, which includes her recollections of the Irish Famine. There is also a collection of printed works, not otherwise held by Cambridge University Library, by Sir Stephen and Aubrey de Vere. The former includes a private printing of Grave and gay: verses of many years, complete with eight pages of manuscript poems in the author's hand.
Part I: Monsell's correspondence.
Part II: Monsell's drawings, paintings, illustrations and artwork for books and other works.
Part III: Monsell's plays, operas and musical works together with stage and costume designs.
Part IV: Family correspondence and papers.