The NCERT literally means The National Council of Education Research and Training; it was established in 1961 to create a common programme of school education. The NCERT designs textbooks, support material, training programmes etc. to meet the diverse needs of the country. Based on NCERT designed syllabus and text books individual state boards create books. Therefore preparing for competitive exams without NCERT text books is not easy.
Books published by NCERT are also used by Central governments schools of Central Board of Secondary Education (CBSE) and are helpful for the preparation of state MPSC Exams, UPSC, Civil Services Exams, Railways Exams, Bank Exams and Other Competitive Exams. These text books are created after thorough research and hard work of numerous scholars, all these text books are available here.
If we analyse the examination pattern, syllabus, and question paper of all the UPSC examinations (Civil services, CDS – Combined Defence Services, NDA, CAPF etc.) we come to this conclusion that NCERT textbook are the best source to start your studies. Even if we read UPSC websites it categorically mentions the difficulty of the subject up till standard 12th which means NCERT books also known as CBSE textbooks.

All the scholars who have cleared the examinations also highly recommend the use of NCERT textbooks as their primary source. Having said this we are also supposed to refer many reference books which list is provided here.
Hope you will not ignore NCERT books while preparing for competitive exams, don’t just depend on single source of information but don’t overexert to find multiple sources. First understand detailed syllabus for exam you are preparing and then get the books as per the syllabus. Many questions in competitive exams were asked straight from these books but don’t be in under impression that all questions will be from these test books.