Versnel is important for his dogged critiques of the dogmas that scholars use to blind themselves to the sheer complexity of polytheistic belief and practice in ancient Greece. Where he is wrong is in thinking that no more adequate conceptual structures are available. He pays lip service to being as critical of the historicist reduction of Hellenic polytheism to mere chaos as he is of the rigid systematizing of the structuralists, but it is hard to imagine a theory regarding polytheism that would not arouse his animosity if it did not take back its claims as quickly as it made them.
However, insofar as any more adequate theorization of polytheism will inevitably require clearing away a great mass of obstructing conventional wisdom in order to even gain a hearing, Versnel's labor of undermining is indispensible. This is perhaps most of all the case regarding his treatment of so-called "henotheism", which however largely reprises in condensed form his earlier account in Inconsistencies in Greek and Roman Religion I: Ter Unus: Isis, Dionysos, Hermes, Three Studies in Henotheism.
There is as usual a good deal of Versnel's patrician raillery which is tiresome beyond measure, and some chapters go well beyond their needed length due to verbosity, frivolous footnotes and an utter incapacity to recognize when a point has been made. Versnel has a generalized contempt for religious experience which ill befits a scholar of religion, but this attitude seems to be all that permits the typical modern scholar to view ancient polytheisms with any sort of equanimity, rather than as a partisan of monotheism.
This book has some super interesting passages, but most of it is just long. Everything is dragged out and repeated (as is often my complaint with academic writing), yet Versnel still managed to leap to conclusions. The translation of German/Greek/Dutch is also inconsistent. Sometimes translated, sometimes not.