These books are excellent, and any reason for using them is given extra weight given that they can be purchased used from Amazon at such a reduced price.
The books deal with all aspects of grammar (and have even taught me a few things, and I'm a grammar teacher! I guess no teacher is complete, especially in relation to techniques).
I would recommend all of these books, I use the elementary, the lower intermediate, the intermediate and upper intermediate. The only sadness is that the publishers have never seen the sense in completing the series with an advanced books that deals with far more elaborate and literary language on the one hand, and technical and specialised language on the other. The books in the series that exist so far are however priceless and well worth the investment, as much for teacher as for students.