The Monmouthshire Antiquarian Association (formerly called the Monmouthshire and Caerleon Antiquarian Association) have published a number of free standing monographs, some of which can be found online:
Morgan, Octavius & Wakeman, Thomas – Wentwood Castle Troggy and Llanvair Castle. Newport: MCAA, 1863.
Morgan, Octavius & Wakeman, Thomas – Notices of Pencoyd Castle and Langstone. Newport, MCAA, 1864.
Lee, John Edward – Supplement to Isca Silurum or an illustrated catalogue to the Museum of Antiquities, Caerleon. Newport: MCAA, 1868
Morgan, Octavius – Some account of the ancient monuments in the Priory Church Abergavenny. Newport: MCAA, 1872.
Mitchell, Elizabeth Harcourt – The crosses of Monmouthshire. Newport: MCA, 1893.
Morgan, Octavius & Wakeman, Thomas – The monastery of Austin Friars at Newport, with notes on the house at Black Friars and other minor ecclesiastical establishment. Newport: John Edward Lee, 1959.