There are many books available in market but here are some of the books you can prefer given below.
Lucent’s General Knowledge
General Knowledge & Awareness for RRB Railway Recruitment Exams (NTPC/ALP/ASM/Technical)
NCERT books of class - IX and X (History, Economics, Geography and Political Science)
let me clear your doubt.
here I am providing you list of some best books which you can prefer for railway exam. These are
1.RRB Group D Guide by Arihant Experts
2.Railway Recruitment Board (RRB) Group-D (CBT)
3.Indian Railways: Group 'D' Recruitment Exam Guide (Popular Master Guide)
4.Railway Recruitment Cell Group 'D' Exam Practice Work Book
I hope my answer will be helpful for you