Revise? Or advise?

The following is a shorter version of an entry at my other blog, which chronicles the editing of a specific book. 

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One of the things I seem to be able to do, after having had a few exchanges with an author, is to sense where the line is between simply performing edits myself, even if they are substantial, and sending a section or a chapter back to the author with my thoughts and observations. Deciding whether to perform a particular edit myself or to send it back to the author has to do with my comfort level on matters such as these:

_Do I understand what the author is trying to do at this point in the book?

_Do I know what the book ought to be doing at this point? (Sometimes these are not the same thing, which can raise another level of questions about whether to consult with the author or just press ahead.)

_Is there material in this chapter or section that has ramifications for chapters that have already been edited or perhaps are in the process of being revised by the author pursuant to suggestions I sent earlier?

_Given all this, does it make more sense for me to work on this section or chapter, or to return it to the author with my suggestions and observations?