For quant, standard books like R.S. Aggarwal’s Quantitative Aptitude cover the basics well. For reasoning, R.S. Aggarwal’s Verbal and Non-Verbal Reasoning is widely used. For English, S.P. Bakshi’s Objective General English plus daily reading helps. For general awareness, Lucent’s General Knowledge is a popular one-book source. Along with books, previous-year SSC papers and regular mock tests matter more than collecting too many books.