To prepare for Engineering Services, it is very important to understand demands of the exam. The IES exam pattern demands theoretical and numerical understanding of the subject. For Preliminary or stage-I exam i.e. the objective paper you require proper time management and lot of practice of objective questions from several standard books. The Selection of Standard books plays the most significant role for preparation and use your books as your reference notes and mark with different color depending on importance of topic you think is important and would help you in revision further.