It is always a risk to write a book about a book that an author never managed to write. Borges was a genius at this, with his tales of impossible encyclopedias, or literary traces of lost texts that only exist in references found in other texts that—turn out not to exist. Such tales consistently evoke that fascination, even wonder, that accompanies our speculation on anything that could have been written, but wasn’t; or perhaps that could not have been written, but was anyway. And in fact the question of the very possibility of the unwritten book here in question—Edmund Husserl’s “System of Phenomenological Philosophy”—haunts Bob Sandmeyer’s very thorough and helpful reconstruction of the motivations, plans, and ultimate failures of Husserl’s project to bring his life’s work to the pinnacle of a genuinely systematic presentation.