We might say that the Reformed doctrine of the covenant of works, or better, adherence to the doctrine, is recovering from an illness. The doctrine itself is fine. It is what it has long been but from the early 20th century until nearly the end of that century the covenant of works was almost lost among Reformed professing Christians. This happened for a variety of reasons. In some cases the doctrine lost favor (no pun intended) because Modernists wanted to redefine Christianity as only a religion of love. In the theology of the Swiss Reformed theologian Karl Barth (1886–1968), universal electing grace swallowed up creation (nature) and obliterated the covenant of grace. We should not be surprised, thus, to learn that he also rejected the distinction between law and gospel.
More conservative writers also rejected the covenant of work on the ground that the disproportionality between God and man means that it is impossible for God to enter into a covenant of works with his creatures. As a consequence, by the mid-twentieth century it was difficult to find a confessional Reformed theologian teaching the covenant of works. The first popular English-language survey rejected not only the covenant of works as contrary to Scripture but also the covenant of redemption (pactum salutis but rejecting two-thirds of traditional Reformed covenant theology. Those who learned their covenant theology between c. 1950 and 2005 it was difficult to find an introduction to traditional Reformed theology that included the covenant of works.
Here a library of books, essays, podcasts, and source quotations on the history and doctrine of the covenant of works.