Manish Valecha is much better than madan.. If you refer dinesh madan with sm and pm you will not b able to complete this subject.. M. Valecha is well written and easy to learn, all technical tems are explained with examples and diagrams... It is best book for exam. Do this with pm..
Which is the best book to refer for ISCA for self study
ISCA notes in simple english and same structure/language as inst's ISCA module, you can download it in pdf format from www.cafinal.com and the link is https://www.cafinal.com/isca-notes
ISCA we have to swallow and vomit. So , no other options . Just read and read and read. Remember all points . Do some tricks or formula or short form for every points. Practice mannual itself is more than enough to get 60 mark. But the thing is you should study the practice mannual atleast 5 times. Not just reading, careful study .