So, I'm continuing to try to put together a paper on the motivation and significance of Carnap's criticism of Heidegger in his "Overcoming Metaphysics." As I see it, the core is not so much the verification principle as Carnap's anti-authoritarianism; he rejected metaphysics as being an attempt to claim the authority of Truth for value judgments, and considered Heidegger an important contemporary representative of such authoritarian trends.
Part of this project requires me to get a much better grip on Heidegger. After all, Carnap himself spent a long time studying Heidegger before he first presented his anti-Heidegger polemic. However, I find Heidegger extremely hard to understand (probably far more so than Carnap did, since Carnap was familiar with Husserl and the neo-Kantians and the general German philosophical scene which he shared with Heidegger). I've tried reading Heidegger's own writings before, and haven't gotten much out of them, so before attempting that again I'm trying to find other readings that might help me figure out what he's really trying to say.
To that end, I've been reading Husserl's introduction to phenomenology, but I have also found that very hard to follow. Tracing things back further, I looked up some Brentano, which seemed easier to follow, but didn't seem to help much with understanding Husserl. Probably I should read some neo-Kantian stuff, or perhaps work from the other direction and read some Sartre, since I never found Sartre as hard to follow as some other continental thinkers. Maybe seeing what Sartre tries to do with Heidegger will give me more of an idea of what Heidegger could have been up to.
I did pick up a book on Nietzsche's influence on the early 20th century German left wing, particularly the Expressionists. That's also useful for my general thesis, as I find Carnap's approving comments on Nietzsche supportive of my interpretation of Carnap as anti-authoritarian. Nietzsche's criticisms of metaphysics were certainly directed at the way metaphysicians tried to derive authority from Truth, and the appropriation of Nietzsche by other early 20th century leftists shows that Carnap could easily have picked up on that feature of Nietzsche through his leftist cohorts.
Anyway, suggestions from others are of course welcome.