I believe that the author by whole means complete. Complete is the sense that the story line carries well from beginning to end. This is the same sense of saying that the story contains a whole idea, or a coherent plot which plays out well.

Solid is the sense of substantial, or well filled out in each moment of the story. The opposite, to my mind, would be thin or weak or a similar word.

This seems to be a formulation used by some creative writing teachers and writers on the dramatic arts:

Vorhaus provides a number of useful tools and exercises throughout the book, but the part that had the most impact on me was “The Comic Throughline” in Chapter 7, where Vorhaus describes the key elements in a successful comedic story.

Given his desire to experiment with many different story ideas (The Rule of Nine), Vorhause wanted

"a way of writing the barest bones of my story in ten sentences or less, so that I could discover with a minimum of work whether I had an interesting, whole and solid story or not. (p. 76)"
http://heatherhedinsingh.blogspot.com/2010/03/book-review-co...

"Now, casting time as a central enemy to one's work, one's spirit, one's enjoyment of life, is an understandable prejudice for a journalist. As a newspaper reporter, Hemingway "told what happened and, with one trick and another, you communicated the emotion aided by the element of timelines which gives a certain emotion to any account of something that has happened that day" (1932, 2). The apparent urgency of the information swindles the reader into Imagining it, but a month later the time element is gone and the account is forgotten. "But if you make it up instead of describe it you can make it round and whole and solid and give it life" (1967a, 215-16). Then and only then is it worth remembering. Moreover, the constraints of time virtually ensure that a reporter might be able to learn what happened but seldom why it happened (Hotchner 1959, 10)."
http://www.english.upenn.edu/~despey/heming.htm

This above discussion of newspaper reporting vs dramatized events helps fill out this idea of whole and solid. Newspaper reporting because of time and space constraints can not present a sense of the cause of actions so it does not print either a whole idea or story, not does it present a solid, or well filled out motion of how the story unfolds.




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Note added at 45 mins (2010-04-07 16:53:04 GMT)
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not motion of how, but notion of how. But the unfolding is the motion, so to speak.

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Note added at 1 hr (2010-04-07 17:53:45 GMT)
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This is a further discussion from the Yale University on Hemingway's idea of "whole and solid." The whole article may be of some use to you.

"It is an issue that has been puzzling us, especially during the past year. What is it about drama that causes students to react so enthusiastically? Can we utilize this enthusiasm and the vehicle of drama to attain certain classroom teaching objectives that have eluded us by other means? Is it possible that our students see and feel, even when we sometimes cannot, the roundness, the solidity, those life giving qualities of drama that make it appealing?"
http://www.yale.edu/ynhti/curriculum/units/1980/3/80.03.05.x...