A Books not only prepare a platform for the preparation but also hike the confidence level of the student, which is a key to the success. If the students wish to prepare themselves for GATE exam without going for anycoaching then you must study the standard books thoroughly.
Along with the books you should also go through the previous year questions, this gives an idea of asking questions.
Network Analysis: Van Valkenburg
Network and Systems: D. Roy Choudhary
Integrated Electronics: Jacob Milman & C. Halkias, Millman & Grabel
Integrated Circuits: K.R. Botkar
Op. Amps & Linear Integrated Circuit: Gayakwad
Digital Logic & Computer Design: Moris Mano
Signals and System: Oppehum, Willsky & Nacob
Automatic Control System: Benjamin C. Kuo
Control System Engineering: Nagrath & Gopal
Principle of Communication System: Taub & Schilling
Communication System: A. Bruu Carlson
Electromagnetic Waves & Radiating Systems: Jardon & Balmain, JD Kraus