Only four volumes of this set are in print. The other six are rare and hard to find, but I've found most of them through secondhand shopping online.
Volume One: Genesis-Exodus. This volume has an introduction to the set, and then his explication of the main themes of Genesis and Exodus. This is not a commentary per se, but rather a retelling of the narrative so that we can grasp the broad arc of the story. It was very helpful in this regard. He has very few missteps in the text. The biggest thing for me was constantly harping on the patriarchs for supposed sins that aren't really sins (just read James Jordan, Primeval Saints). But then Van der Waal was writing before Jordan, so we can't really blame him. He writes from the refreshing perspective of Dutch Reformed theology, and so rejects the law/gospel divide, the faith/works divide, and emphasizes the unity of the Bible and the unity of the covenant. Great stuff.
This volume surveys Matthew through Luke. The book is worth getting if only for the treatment of the Olivet Discourse. These volumes are very well written, lucid and extremely accessible.
This is volume 1 of a 10 volume series. It is not a commentary, per se, but rather a quick run through the main themes of the books from the covenantal viewpoint. Simple, concise and clear. The original work was written in Dutch under the title "Sola Scriptura." This volume begins with a short defense of the Reformed doctrine of Scripture, then looks at Genesis and Exodus.