Amy Slagle has some answers, as noted here: http://easternchristianbooks.blogspot.com/2011/10/orthodoxy-in-spiritual-marketplace.html

This seems focused on the movement of Protestants (and to some extent, Roman Catholics) towards the Orthodox Church. Does she look at the phenomenon of Greek Catholics who join the Orthodox Church, or the role of the Greek Catholic Churches as "halfway houses" for Roman Catholics on their way down the Tiber to Constantinople?

She does treat Greek Catholics who become Orthodox, but briefly and historically. Not all the converts she interviewed were Protestants by any means. Some were, but some came from Buddhism or not particular religious tradition as such.

I take it, then, that she deals with St. Alexis Toth and the celibacy controversies of the 1890s and 1930s, but not with the phenomenon of individual Greek Catholics becoming Orthodox, which to me is a more interesting question, since it touches upon the Greek Catholic self-image and the success of the Catholic Church's post-conciliar efforts at restoration of the authentic Traditions of the Eastern Catholic Churches. Most of the Greek Catholics I know who became Orthodox did so because they felt that being Greek Catholic required too many compromises with Latin doctrine, or, if they were unwilling to compromise, felt their spiritual integrity threatened by effort needed to balance the conflicting requirements imposed by the Vatican. Interestingly, a lot of these people were originally either Protestants or Roman Catholics, which is why I speak of the Greek Catholic Churches as "halfway houses" for them.

Sounds like an interesting book. Being a convert myself, it has certainly been an interesting experience. I have seen a number of different experiences and backgrounds in the various people I've met.