Books I recommend

Books I recommend  for gate preparation

COMPILERS

Compilers : Principles, Techniques , Alfred V. Aho, Compiler design O.G kakde http://lambda.uta.edu/cse5317/notes/node1.html

THEORY OF COMPUTATION

Introduction to Automata Theory, Languages and Computation , John E. Hopcroft,

Formal Languages And Automata Theory , K V N Sunitha, N Kalyani 

OPERATING SYSTEM

Operating System Concepts by Galvin,Silberswatz 

SCHAUM SERIES , Archer J Harris 

DATA STRUCTURE

Data StructuresandProgram Designin C++ Prentice Hall ,Robert L. Kruse Alexander

Data Structures (Schaum’s Outline Series) by Seymore Lipshutz 

Fundamentals of Data Structures in C 2nd by Sartaj Sahni

DIGITAL LOGIC 

Digital Logic Design by Morris Mano

Fundamentals of digital circuit by anand kumar 

COMPUTER ARCHITECTURE 

Computer System Architecture by Morris Mano

fundamental of computer architecture , Mostafa Abd-El-Barr ,Hesham El-Rewini 

COMPUTER NETWORKS

computer networks by Andrew S Tanenbaum 

DATABASE

Database System Concepts by Korth,Sudershan & Silberswatz

Fundamental Of Database Systems by Elmsari, Navathe

Schaum's Outline of Fundamentals of Relational Databases 

ALGORITHM

Introduction to Algorithms , CLRS

Algorithms , Dasgupta ,vazirani 

MATHS

Elements of Discrete Mathematics : C l Liu

Introduction to Graph Theory , Douglas B. West 

Higher Engineering Mathematics B,S grewal // one serious advise don't read this book crappy book only good if you already know maths no learning curve. good alternative for this will be Advanced Engineering Mathematics by Erwin Kreyszig 

Software/web tech/aptitude/English is more or less like general knowledge 

Some books  may not be the best book but they are very easy to understand and will develop your interest.