Here are some recommended books for SSC CHSL exam preparation: English Preparation: Objective General English by S.P. Bakshi Word Power Made Easy by Norman Lewis A Mirror of Common Errors by A.K. Singh\
General Studies (GS) Preparation Lucent's General Knowledge Manorama Yearbook NCERT Books: MUST
According to me, For Maths: Kiran publication, RS Agrawal For English: SP Bakshi, Mirror of common errors For Reasoning: practice from previous year papers For GS: study each topic carefully from trusted source and learn current affairs. That is all !