See reading all the materials and stuff is quite costly as well as time taking. Now depending on the time you have, you have to choose wisely. You know your subjects, if you think that you can get the syllabus done and can provide the answer asked in the exam by reading one book then its absolutely fine. But in general no book is perfect. So every book has its own advantage and disadvantages. Thus to minimize all this disadvantages use of multiple books is appreciated. Now if you can get the books from library or PDF versions or any way out, you can look at them and choose the material which will be based for you. Studying material thoroughly is important.

I hope this answer gives you some perspective. All the very best for your future endeavors!