Hello dear student,

I would suggest you to buy a general knowledge book which is that will help you with the GK questions. And then you should buy a book of reasoning and aptitude pictures that will help you to improve your aptitude questions. Why you asking for a book then I would like to recommend you pathfinder CDS it is one of the best books you can and have for the preparation. While for afcat you can buy Aarihant's afcat book for preparation. I hope this was helpful to you.

Best wishes