It greatly depends. In classrooms and JLPT prep courses, you'll notice the Shinkanzen textbook series are used the most. For those who are self-studying, the Try! JLPT N2, Nihongo Sou Matome and Goukaku Dekiru are popular choices — although it comes down to your preference.
Lastly, the 2500 Essential Vocabulary for the JLPT N2 is a great filler to get all vocabulary. It's a small vocabulary book, so we see a lot of students bring it to their work, read it on trains or study it on their break.