Helo aspirant., Its good to know that you wanted to be a civil servant. Have patience while preparing for this exam as you would face a lot of difficulties in this journey. I have mentioned the link below, you can go through it . It is the book written by Mrs ila tripathi. She has explained very well about how to prepare for ias exam .tbis book is available free on Kindle just go through it. I hope it may help you. click here

Hello,

Please specify the name of the exam so we can mention the best books that are available for the same.

Hello Simran,
In competitive exams for government jobs, generally questions are asked from Quantitative aptitude, English Language, Reasoning, General Awareness. Kindly mention you are preparing for which exam so I can recommend you the books accordingly.
Good Luck!