One of the most stimulating works on infant baptism that I’ve found is Kurt Stasiak’s Return to Grace: A Theology for Infant Baptism . Stasiak is a Roman Catholic theologian who teaches liturgics at St Meinrad School of Theology. The first half of the book is a discussion of the debates surrounding infant and adult baptism in the Catholic church since Vatican II. The second part is a theology of infant baptism organized around a theology of childhood and baptism conceived as an act of adoption. There is a lot of solid biblical exegesis (including a citation of Ridderbos!). Stasiak’s treatment has some specifically Catholic colorations, but overall it’s an ecumenically viable treatment of infant baptism.