Shubhankar Dam, who teaching at the Singapore Management University (SMU), has a forthcoming book Presidential Legislation in India: The Law and Practice of Ordinances which is now available for pre-order on Amazon. The book is published by Cambridge University Press, as part of an exciting new series on Comparative Constitutional Law and Policy. (I suspect that a cheaper South Asian edition of the book will be available when it's published.) The topic is a vital one, and I can't recall any serious contribution on this subject other than two important books by DC Wadhwa. I've only glanced through the Table of Contents -- but even that quick perusal seems sufficient to confirm that the book looks extremely exciting and promises to be a very significant contribution to Indian constitutional law scholarship.