I don't really know what Views From the Oldest House is about. I've read it twice now, and enjoyed it both times. I even enjoyed it more the second time than the first, despite my surprise at not understanding it better. I'm not sure whether it's intensely clever and deeply layered allegory, or stream-of-literary-consciousness vaguery, but it doesn't bother me. As with Grant's Rumors of Spring, I suspect it works because the key characters in the story don't have any more idea of what's going on than we do - even the ones who pretend to omniscience are faking.
Clearly there's a lot about religion going on here, but it's neither obvious nor heavy handed. You can read all sorts of things in if you want to. If you don't, that's fine too. One of the points of the book may be that it doesn't really matter. You can read it as metaphor for duality, consciousness, pretense, personality, or all sorts of other things, with warnings about global warming thrown in for free.
It sounds terrible, doesn't it? Stuffy, pretentious, and dull. Yet it's not any of those things. Instead, it's a delightful and confusing parable (about something) that's beautifully written, with a friendly tone that goes out of its way to engage you. If you like intelligent SFF, try this. If you don't need determinate, clear-cut conclusions, this is for you. If you've never wandered far from Heinlein, this may not be your thing, but if you have at least a small sense of adventure, I recommend this.