Hope against Hope: Christian Eschatology at the Turn of the Millennium
by Richard Bauckham and Trevor Hart
Bauckham is a leading scholar on the book of Revelation and clearly describes his hope of universalism in Hope against Hope: Christian Eschatology at the Turn of the Millennium.
Other related books by Bauckham include:
The Theology of the Book of Revelation (New Testament Theology)
Climax of Prophecy: Studies on the Book of Revelation
By the way, Robin Parry says that Bauckham is one of his favorite scholars.