M A James wrote a nature book, The Circling Year (1939), on what to look for month by month, and a play for children, The Crooked Crowns (1940). He, or indeed, she, as I have been able to find no biographical information as yet, also wrote one pony book, a pony autobiography.
Finding the book
Not the easiest of titles to track down, particularly with its dustjacket. Pricing can be erratic.
Links and sources
British Library Catalogue
Thanks to Lisa Catz for the photograph, and for the information on the plot.