A couple of thoughts: While Time Enough for Love is set aside for a reread soon, personally I'd prefer holding off on that one, as I've set it aside to read as part of the "future history" series. However, I'm not going to oppose it particularly strongly, either... I just may not do a reread before the discussion happens.
As for what book to pick -- aside from restored Puppet Masters, as far as I know, I have all of his work that might come up (with the exception of his political book, Take Back Your Government, etc. -- which I would have, but it's ridiculously priced at the moment!). All my Heinlein is out of storage and on the shelves, so I don't think there's anything missing aside from this one.
And Mollygurl: that quote on History sounds a heck of a lot like Dr. Johnson's opinion on the subject -- I would not at all doubt it's a nod to the good Doctor, as I've run into other things in Heinlein here and there that indicate he had a strong respect for him, and agreed with him on different matters....
By the way... it's been too long since I read Job to remember it that well (not since it was first published, as a matter of fact)... but as I recall, it seemed to be rather influenced by Cabell's work, especially Jurgen (which some of Heinlein's characters did not approve, though I get the impression Heinlein quite enjoyed it) -- not so much in style, or even subject matter, but more in that it was an homage to some of the things Cabell had done....