ICAI's Study material will only fetch u marks in ISCA. U may refer Dinesh madan for conceptual understanding in some topics (as not all topis are conceptually explained to keep the books size manageable). Again Rishabh Pugalia sir's book is also good. It is just a copy paste of ICAI's study material but it contains some helpful features like all RTP questions at one place, all previous years questions, neumonics, case based questions etc. The advavatage of this book is that u are getting the institute's language instead of some other author's language, so it is as good as ICAI's study material along with the added advantage of the additional features mentioned by me . The disadvantage is that if u cant understand ICAI's study material then u cant understand this book also.
Further u can visit my blog which i recently created to creat a forum of discussion and sharing knowledge. U may put ur queries on ISCA on my Blog and i will be happy to help . The address of my blog is : https://www.blogger.com/blogger.g?blogID=1606766854238907809#editor/target=post;postID=8182046767432510060;onPublishedMenu=pages;onClosedMenu=pages;postNum=0;src=postname Jai Hind