An all-around failure.

First, by trying to tie this much more to apocalypses written later, as in the ones found at Nag Hammadi, rather than ones written before this or at the same time, as in ones found at Qumran, Pagels has shown that she wants to ride her Gnosticism one-trick pony as part of her critique. This is only increased by her repeated referencing of Karen King, albeit before King's sinking into academic scandal.

Second, I reject her theory of compositional history. While I don't think all of Revelation was written in Neronian times, I think a central non-Christian core was. In what's a light book anyway, Pagels is definitely light on compositional history issues.

Third, no, Athanasius and the Council of Nicaea did not close the Christian canon. At minimum, that's misinformation. At maximum, that's a bald-faced lie; in general, "denominations" of the Church of the East omit bits of books at the back end of the New Testament ... including Revelation in some cases! And, given the fact that she references another author to talk about the Ethiopian church adding 1 Enoch, she knows this is untrue. In the case of the Church of the East, it starts with the Peshitta, which excludes 2 Peter, 2 and 3 John, Jude and Revelation. This was pre-Chalcedon and pre-split, and was the canon accepted by John Chrysostom.