Isca help

Hello people, i request you to please help me in my query. 

I gave my final exams for the first time in Nov 13 where i got 26 in ISCA. I assumed my preparation wasn't right and i studied the ICAI material thouroughly and made my own notes for each and every chapter. I gave my exam again in May 14, where had i cleared ISCA i would have been a CA by now. I got 28 and i am truly in deep worry as i thought i had done enough to get an exemption. I gave a good examination but the result doesn't show. 

I request you guys to please help me as to which is a better book than the Institute study material. I revised the practice manual about 3 times already for the previous examination. 

There could be a problem with my presentation skills but i presented as per the practice manual and there is nothing more i could have done. My friends have recommended that i read Manish Valecha's book.

Is the change worth it? Am i making a mistake somewhere?

A little about myself, i can't memorize easily. I give more importance to understanding the subject and then answering in my own words. 

Thank you so much for your help.