Hello,

For General Knowledge and Current Affairs, you can use Lucent's GK for static portion,for dynamic portion the best is to read newspaper such as The Hindu or Indian Express, or any other magazine such as Pratiyogita Darpan, you can also find monthly compilations in lot of websites online. For Numerical Ability, you can use ,Quantitative Aptitude by RS Agarwal or NCERT book. For Mental Ability, you can refer any standard Reasoning book such as one by RK Agarwal or S Chand. For language comprehension use any standard grammar book along with Word Power Made Easy,this little book will help you a lot in vocabulary building.

For previous years paper, visit; http://bhuonline.in/old-qus-paper-2019.html