I highly recommend these textbooks, of which there are four (vocabulary, reading, listening and grammar). The author is clearly someone who has thought about the best approach to help students not only understand, but also remember the key points and strategies for the TOEIC test. If you are currently under 500 points I would recommend this series of four books. IF you are over 500, then you will likely know most of this anyway so would be better off with something more advanced.