Well to be very honest reading book line by line would be a great deal of efforts and time. But yeah it will ensure that you will become very much conceptual about each topic if you understand them well. Also from my perspective GATE AUTHORITIES in the recent years have formed MSQ's as the backbone of the exam.
But for subjects like Algorithms or Theory of Computation or Graph Theory I will advise you to join a course because going through the standards book will take a huge amount of your time in just understanding the concepts because they are much detailed with things that are irrelevant to exam. However, still if you want you can go ahead and learn from the standard books as nothing is best than the original sources.
