There are many reference books in the market that the candidates can choose from. However, when it comes to the preparation for an exam like GATE, one should follow the text that is easy to follow and covers the entire details of the GATE Syllabus 2020. The following books are popularly followed by the prospective candidates for the preparation of the GATE Exam.

Reference Books
1.TOC and Compilers (Compilers: Principles, Techniques, and Tools) by J.D. Ullman.
2.Database Management Systems – DBMS by Korth.
3.Computer Algorithms by Ellis Horowitz.
4.Operating Systems Concepts (OS) by Peter Baer Galvin.
5.Data Communications and Networking by Behrouz A. Forouzan.
6.Digital Logic and Computer Design by Morris Mano.

Also worthy of special mentioned are many books that the candidates refer frequently in the preparation of various topics.
1.Matrices by Vasista
2.Higher Engineering Maths by BS Grewal
3.Probability and Statistics by Miller and Freund.
4.Discrete Mathematical Structures by Trembly and Manohar
5.Discrete Mathematical Structures by Kolman, Busby and Ross
6.Graph Theory by Narsingh Deo
7.Numerical Methods by Grewal
8.Introduction to Computer Theory by Daniel Cohen
9.Automata by Ullman and Hopcroft.
10.Theory of Computer Science by Chandrasekaran and Mishra
Following the above reference books can put you in a good standing for acing your GATE CSE 2020 Exam.