Dieter Mehl 
The Middle English Romances of the Thirteenth and Fourteenth Centuries (Routledge Revivals) [PDF ebook] 

First published in English in 1968, this book provides a critical guide to the wide field of the Middle English Romances and gives a helpful survey of the contemporary state of scholarship. Dr Mehl traces the development of Middle English Romances from thee thirteenth to the end of the fourteenth century, and interprets a number of these romances. The emphasis is literary, on their form and dominant themes rather than source-material or language.