To me, here's what's implied by the passage:

• Brett, a woman, went on a trip hoping for some nookie with Robert Cohn. Robert did not come onto Brett, at least not to the extent she was hoping, and she was disappointed.

  Now Brett is trying to pump Jake for information about Robert. Because she still wants to get Robert in bed. She's also annoyed because Robert is, evidently, going on another trip with someone else.

  And, she's offended that Jake said 'Congratulations,' regarding the trip she went on with Robert, because that implies that Robert is out of her league. Which fits with her paranoia re: Why didn't Robert come onto her? (She gave him every chance, after all, even took him to San Sebastian. How much more obvious could she have been??? San Sebastian!

  Then Jake insults her by implying that if she really wants guys to come onto ladies more easily, she should become a prostitute.

  And she smacks him verbally for that.

^^ that's the subtext I see.

Galastel, you asked why is it brilliant?

Maybe it is, maybe it isn't, everyone will have their own response, but my Answer is this:

It's brilliant because it engages a different part of the brain. It requires active reading and putting pieces together.

Additional answer: Stories that excite different parts of the brain at different times and with different intensities in an orchestrated way are generally more fully realized. To me this means better.

It's also fairly obvious that Hemingway users every word intentionally. Ex: Brett could be a man's name, so he gives the tag, 'she said.' That's an example of intention to word usage.

To me, here's what's implied by the passage:

• Brett, a woman, went on a trip hoping for some nookie with Robert Cohn. Robert did not come onto Brett, at least not to the extent she was hoping, and she was disappointed.

  Now Brett is trying to pump Jake for information about Robert. Because she still wants to get Robert in bed. She's also annoyed because Robert is, evidently, going on another trip with someone else.

  And, she's offended that Jake said 'Congratulations,' regarding the trip she went on with Robert, because that implies that Robert is out of her league. Which fits with her paranoia re: Why didn't Robert come onto her? (She gave him every chance, after all, even took him to San Sebastian. How much more obvious could she have been??? San Sebastian!

  Then Jake insults her by implying that if she really wants guys to come onto ladies more easily, she should become a prostitute.

  And she smacks him verbally for that.

^^ that's the subtext I see.

Galastel, you asked why is it brilliant?

Maybe it is, maybe it isn't, everyone will have their own response, but my Answer is this:

It's brilliant because it engages a different part of the brain. It requires active reading and putting pieces together.

Additional answer: Stories that excite different parts of the brain at different times and with different intensities in an orchestrated way are generally more fully realized. To me this means better.

It's also fairly obvious that Hemingway users every word intentionally. Ex: Brett could be a man's name, so he gives the tag, 'she said.' That's an example of intention to word usage.

EDIT: I've seen some of this boom-boom-boom done (with the leapfrog-type, subtext-type dialog) done in smaller chunks by modern writers. Example: First third of page 13 in How to Stop Time (look inside on Amazon.). You aren't really sure what they're talking about, but the feel of it is immediate, they know what they're talking about, and you want to be in on the secret, whatever it is. I think it can work well and is a useful way to inject a little almost-intrigue.