This is not a book which sets out to describe or explain the institution of the triumph, but rather to interrogate how we 'do' history, especially when all the sources that we rely upon have an agenda of their own. The triumph, then, is used here as an example of the slippery nature of reconstructing an alien culture, which can only be done through others' previous reconstructions.
Beard can be quite eccentric but this is a fascinating book which follows up on some of the discussions she sketched out in her Classics: A Very Short Introduction. I wonder if the negative reviews are the result of a mis-targeting of this books for a 'general' audience when it actually engages with, and is sited within, academic arguments that are of pressing interest to history and classics scholars?
This does include a detailed description of Pompey's great triumph but then goes on to question all the things that we think we know, as much from Hollywood representations as from classical texts.
In sum, then, this is an intelligent and enlightening engagement with the idea of the triumph and what it might mean, and be made to mean, at various points in history. But, as one would perhaps expect from a Classics professor, this is far more than a descriptive 'history' book. Excellent for older undergraduates and postgraduates or anyone interested in the construction of history. But perhaps a bit hollow for anyone looking for the 'reality' or unproblematic facts of the past.