A book published by the Roade Local History Society entitled 'Roade through the camera', ISBN 978-0-9563496-0-6, 2009 has a small piece on the SMJ in Chapter 12: Railways.
There are two photos; the first of a goods train heading toward the SMJ spur taken in Aug 1890 and the second of the construction of the SMJ bay at Roade station c.1890. There is an accompanying diagram of the LNWR and the SMJ through Roade. Intrestingly for industrial railway historians there is a tramway shown descending to the LNWR from the lime pits which stood where Pianoforte factory now stands (albeit empty). Knowledge of this tramway and information on these pits is scarce. The diagram is detailed and shows individual lines, such as the double tracked SMJ spur and sidings.
The text consists of only a paragraph that describes the SMJ's route through the village and the purpose of the railway. Apparently the SMJ was known locally as the 'slow, miserable and jolty', the 'linger and die' and the 'bread and herring'. It was also known as 'the scratter', the book questions whether this final nickname had any connections to a traditional cider apple masher. Having asked people of more advanced years than me, Northamptonshire does not have a cider heritage so I would estimate there is no connection.
The book is mainly photographic with accompanying descriptions rather than text-rich. Understandably the subject of railways mainly concerns Roade Cutting and the long-gone station.