I will suggest not to read GK publishers book. These are just waste of time and money.

For GATE Exam problem solving is very important. If you can solve problem you can crack the GATE EXam. For problem point of view RK Kanodia's books are excellent resource. These book has awesome problem with full solution.

ou must do prepration along with your semester study. Read the theory from your text books and solve problems from the gate by rk kanodia book. this is the best method for prepration. If you find the problem to solve dificult, dont worry full solution is there.