How to prepare for network theory gate 

Network theory or circuit theory is one of most important subject for an electrical or electronics engineer as this subject is the base to all other subject with their respective branch. This subject provides confidence in numerical solving ability.

Syllabus for network theory for gate is as:-

Nodal and mesh analysis; Network theorems: superposition, Thevenin and Norton’s, maximum power transfer; Wye‐Delta transformation; Steady state sinusoidal analysis using phasors; Time domain analysis of simple linear circuits; Solution of network equations using Laplace transform; Frequency domain analysis of RLC circuits; Linear 2‐port network parameters: driving point and transfer functions; State equations for networks.

Best books to study network theory

Reference books you can follow for studying network theory are-. 

1.Engineering Circuit Analysis  2. “Network Theory”    3.Fundamentals of Electric Circuits 4.Circuit Theory: Analysis & Synthesis 5. Network Analysis

William H. Hayt   A V Bakshi U A.   Charles K. Alexander, Matthew N. O. Sadiku     Abhuijit  Chakrabarti  Mac Van Valkenburg

These were some of the books an aspirant can refer for deep understanding of the subject (network theory).

The best book among them is "fundamental of electric circuits" by alexander and sadiku. The book explains the concepts very deeply.

The network book by Abhijit Chakrabarti is the best book of an indian writer, if you are not good at studying a foreign writer book than you can refer this book and then go for the other standard book.

When i was studying in college i refered this book for my semester exam. And i found it a good book for fresh learners.

At the end, in subject like network or circuit theory, you need to practice questions as much you can to be more fluent with the subject.