Trevor,
I have not read any books by Heidegger on Kant. I presume that such a text would fall within the project overcoming of metaphysics. I suspect that these would have to be after Being and Time, which pretty much finished without seriously venturing into the destruction of the history of western ontology.
I guess the "Kant book" would explore Kant's project in the 3 Critiques as a groundwork for metaphysics, that is, an ontology, rather than the Kant of the First Critique bring forth a theory of knowledge based on science (physics).
Here is a book, Heidegger's Kant and the Problem of Metaphysics
Here is a scholarly link. It looks as if to read read Heidegger on Kant you have to wander through a lot of the Kantian transcendental machinery. Not really my cup of tea.
I presume that Heidegger would be destructuring the traditional approach approach in which the question of the meaning of being is addressed from the perspective of the logic of propositional statements. Implicit in this traditional approach is the thesis that theoretical knowledge represents the most fundamental relation between the human individual and the beings in her surrounding world. It would be argued that theoretical knowledge represents only one kind of intentional conduct, and that it is founded on more fundamental modes of practical engagement with the surrounding world.
That's the approach of Being and Time. I guess a key concern from a philosophical heremenutics position is to try and understand why and how theoretical knowledge came to seem like the most fundamental relation to being. This would take the form of a destructuring (Destruktion) of the philosophical tradition:--in Being and Time it is briefly undertaken in relation to the philosophy of Descartes.Presumably the later texts would destructure the philosophies of Aristotle, Kant, Hegel, and Plato.
As an aside this approach exerted an influence on Derrida ---eg., the deconstructive approach. Of course, there are important differences between the two approaches since Derrida is destructuring Heidegger.
Since I basically accept Heidegger's shift to the everyday, practical knowing and concern I do not have much interest in the epistemologcal concerns of the philosophical tradition. I'm more interested in the way that Division I of Being and Time provides a phenomenology of average everydayness and the way that account is revised in the light of the authentic way of being described in Division II. It seems to me that is here that Heidegger makes a significant difference in how we see the world and ourselves.
As Dreyfus spells it out in his commentary on Division 1 Heidegger’s basic theses are that:
*people have skills for coping with equipment, other people and themselves;
*their shared everyday coping practices conform to norms;
*the interrelated totality of equipment, norms and social roles form a whole which Heidegger calls “significance.”
*Significance is the basis of average intelligibility, and
*this average intelligibility can be further articulated in language.