This book will be impenetrable without prior knowledge of Heidegger and especially Being and Time. The reason for this is that the 'basic problems' explicitly deals with with the "temporal" facet of Heidegger's quest to carve out a path for fundamental-ontology in 'Being and Time'. Now, all of the teachings of Martin Heidegger are temporally based, to put it that way, but the manner in which temporality is described in 'Being and Time' is done with a nuance and scientific vigor that morphes after the 1920's and this is what is often mistakenly called 'The Turn'. What this does is explicitly presupposed the reader with the vast probject of "Being and Time". In this book, the insights of those investigations are explicitly applied to particular stages in the history of ontology, culminating in what is nothing less than a vivisection of Kant.
This book is foremost about the 'ontological difference'. As translated, the 'ontological difference' does indeed consist of entities and their being. However, I think that this English translation by Hofstadter, one that is perhaps initiated by Macquarrie & Robinson [I'm not sure], slightly undermines Heidegger's teachings. This change of being into "Being" obscures Heidegger's investigations because being is not a being. Of course, one could argue that "being" is already an objectification, which is why the word nearly disappears in the late-Heidegger.
There is also the problem of substituting "entities" for "beings". It is true that 'entity' is more common in English; we wouldn't hesitate calling a pen or a social-program an entity, but would we call it a being? We should. The problem is that in English "entity" is very ontical and thus removed, in a sense, from its propriety, the being's being. "Entity" compromises Heidegger's initiative to reveal how the ontical is "always already" existentially in the ontological. By substituting 'beings' for 'entities', so as to arrive at 'the being of a being', we retain the essential continuity of language by directing the being back to its origin.
The frequency in which the term "horizon" appears in this text is only consequential to the elucidation of "Temporality" [estatical-enpresenting]. I think the crucial reason as to why "horizon" becomes increasingly important is because Heidegger's temporal enterprise is, at bottom, an interpretation of "care". Here we can again see why "Being and Time" is so important for this text, since "care" is an eminent facet of "Being and Time". In this case it would perhaps be circumspect to take Heidegger's "Temporality" [estatical-enpresenting] as an attempt to institute "care" itself as a limit-situation, with the "horizons" serving as the literal schematic boundaries which are then maintained by the temporal ecstasies, though this is only a preoccupation of mine. One could perhaps further inquire into how these schema [horizions-praesens] are made manifest, and thus constituted. To impart to you another one of my worthless positions, I was personally heeded from any such inquiry because throughout all the teachings of Heidegger that I've encountered, but especially here, I could hear Nietzsche's cry "back to the body".
EDIT 4/30/2011
I've tried to correct the confusing, anomalous vocabulary and syntax of the initial review without deleting it outright. I'll probably get around to rewriting it so as to totally remove the layer of sophmoric pretension.
In reference to Nietzsche's call, it seems that I heard Heidegger correctly. However, for those who are unsuspecting "body" must be ambiguous. Here is a statement by Heidegger from the third volume of the Nietzsche courses which clears everything up, in case you were confused. This is from page 218 of the third volume (paperback), the second book which is titled as 'The Will to Power as Knowledge and Metaphysics, Nihilism":
"However, the nihilistic [Nietzsche's] negation of reason does not exclude thought (ratio); rather, it relegates thought to the service of animality (animalitas). Yet animality too is likewise already inverted. It no longer passes for mere sensuality and what is base in man. Animality is the body bodying forth, that is replete with its own overwhelming urges. The name body identifies the distinctive unity in the constructs of domination in all drives, urges, and passions that will life itself. Because animality lives only by bodying, it is as will to power".
P.S. I'd like to offer another correction. Since I had mentioned Derrida [i.e., 'Post-Modernism'] in this review I'll just go ahead and say what needs to be said since I merely hinted at it earlier; don't read Derrida at all. He is nothing more than a Leftist hijacking of Nietzsche and Heidegger, which means a direct attack upon Nietzsche and Heidegger. As this he is a monument to mendacity, as all of today's Academia is, and has been for some time.