Orthodox theologian and philosopher David Bentley Hart’s book on universal salvation is arguably the most talked-about book on the subject for years. It is also one of the most head-on defenses of soteriological universalism to hit the mainstream theological audience worldwide.
For those acquainted with the topic, many of Hart’s arguments are classics, based on biblical and theological reasoning, but Hart goes furthest in developing a moral argument for universal salvation based on the fundamental goodness of God. Personally, I did not give much weight to such arguments before, but Hart convincingly argues, that if God is truly good and loving (even requiring us to love our enemies as he himself does!), this must mean the final salvation of all.
Much have been said already on the book (see e.g. the many positive reviews of the book on Eclectic Orthodoxy). I wont add more here, but simply recommend the book. For anyone interested in the topic, this is a must read.