The collection contains several hundred notebooks, notes, lists, cuttings, postcards, essays, theatre programmes and illustrations. The notes and notebooks refer to various subjects including: English language, Beowulf, Sir Gawain and the Green Knight, Tennyson, Shakespeare, philology, plant names, innsigns, geography, chess and heraldry.
Of particular interest is an original manuscript of William Gilpin, Three Essays (published in 1792), with extensive alterations for an intended new edition, which was eventually published posthumously in 1808, with nine original drawings.
The collection also contains:
- an annotated copy of Chronicon Galfridi le Baker de Swynebroke, ed. E.M.Thompson (Oxford, 1889)
- Milton Tercentenary: the portraits, prints and writings of John Milton (Cambridge, 1908), extra-illustrated and annotated by Cyril Brett
- a 1925 edition of Sir Gawain and the Green Knight, edited by J. R. R. Tolkien and E. V. Gordon, together with two holograph letters from Tolkien to Brett relating to the edition