Gould's article is pretty old and this is an area where a lot of progress has been made and continues to be made.
Gould himself changed his mind somewhat (see his book
Wonderful Life). Ironically it seems that he was wrong - it later turned out that the Burgess Shale fauna had been misinterpreted. See Conway-Morris's
The Crucible of Creation. Fortey's
Trilobite has a good chapter on the Cambrian Explosion, too.
Even that is out of date. New discoveries keep turning up now that we know of the phosphatised fossils found in the Doushanto formation.
At present it sems that the Cambrian explosion is to a large extent an artefact of the fossil record - most of the earlier life being too small to show up as ordinary fossils (Fortey got that right).