Real-world example, adapted from 7.02, example 21, using a title that does not already contain the author’s name:

I maintain such a book section in an _authored_ volume should be rendered as:

Freud, S. (1953). The method of interpreting dreams: An analysis of a specimen dream. In S. Freud, _The standard edition of the complete psychological works_ (U. Strachey, Ed. & Trans., Vol. 4, pp. 96—121). London: Vintage.

but not like the following (which obscures the authorship of the book as a whole)

Freud, S. (1953). The method of interpreting dreams: An analysis of a specimen dream. In U. Strachey (Ed. & Trans.), _The standard edition of the complete psychological works_ (Vol. 4, pp. 96—121). London: Vintage.

nor like the following (which fails to draw a clear distinction between the book’s author(s) and editor(s)/translator(s):

Freud, S. (1953). The method of interpreting dreams: An analysis of a specimen dream. In S. Freud, U. Strachey (Ed. & Trans.), _The standard edition of the complete psychological works_ (Vol. 4, pp. 96—121). London: Vintage.

Note that Zotero’s rendering of books is mostly ok, with editor(s)/translator(s) appearing after the title:

Freud, S. (1953). _The standard edition of the complete psychological works._ (U. Strachey, Ed. & Trans.) (Vol. 4). London: Vintage.

(Though, again, example 26 does not show a full stop between the title and the editor/translator information in round brackets. Also, the round brackets used back to back look a bit odd, and the APA manual in fact deems this to be incorrect; see 4.09.)

Here's a comment by an APA editor on their blog that strongly suggests that they generally don't want the book author cited for examples like the Freud above:
http://blog.apastyle.org/apastyle/2013/09/how-to-cite-an-anthology-or-collected-works.html#comment-6a01157041f4e3970b01b8d07d3d3d970c

Even the editors in parenthese that we have for book volumes isn't something ever found in the Manual, so that, too, feels borderline, but I suppose we have to do something about that pretty common case. (The same editor in that comment thread is very specific that the parenthese are for translators--so ex. 26 doesn't necessarily apply).
I'm open to be convinced otherwise, but so far I'm not convinced we should invent APA style variants that I don't see supported by the Manual. For people who want sensible citations, there's always the Chicago Manual :P

As for the back-to-back parentheses. APA does have them in citations occasionally, see e.g. 7.1, example 3, the Gustin v. Mathews case.
The other option here would be to, again, include the volume number into the title, something I'm not really comfortable doing with the citation style (though I suppose it's technically possible). I'm not comfortable including editor and volume in the same parentheses.

The placement of the period wrt editors/translators of books, though, is clearly a bug. I'll fix it.

Thank you, adamsmith & bwiernik, that’s all helpful.

As to avoiding APA for “sensible citations”, I couldn’t agree more – the blog indeed calls for using, e.g.,

> Rieber, R. W., & Carton, A. S. (1987). _The Collected Works of L. S. Vygotsky: Vol. 1. Problems of general psychology_ (N. Minick, Trans.). New York, NY: Plenum Press.

> In text: (Rieber & Carton, 1987)

where everyone in their right mind would put the author, Vygotsky, in front, and use his name for the in-text citation. (And this is not the only example; indeed there’s method in their madness.)

It seems APA have fallen into the trap of selective sampling; every single one of APA’s examples uses a title that already contains the name of the bookauthor – @bwiernik: While you’re at it, could you please ask APA how in the world they are going to cite an authored _and_ edited book where the title does _not_ already contain the name of the bookauthor?

At least I hope Zotero will avoid hard-coding _this_ behaviour into the style file – better let users delete their bookauthors if they _really_ want to follow this madness.

(@adamsmith, if you don't want to read a long discussion of APA style, you can skip to the last paragraph for my recommended change to the CSL style)

Okay, after a long series of emails, I've nailed down APA's preference here. The position is that the purpose of the reference is to direct the reader to the source of the information.

If it is an authored book, the reference should contain only the book, not the chapter that is being cited. The format for "chapter in edited book" is intended solely for books that are anthologies or compilations of work by multiple authors.

So, for example, if I were to cite the introduction to this book (http://www.bartlebysbooks.com/shop/bartleby/59583.html), the reference would simply be:

O’Connor, J. (1984). The last book: Confessions of a gun editor. Clinton, NJ: Amwell Press.

The only reference to the introduction would be in the in-text citation, would might look something like: ” (O’Connor, 1984, Introduction)

For the Reiber and Carton (1987) citation, it would be most correct to cite the specific work of Vyotsky which you are referencing, thus using the format of Example 21 (unless you are referring to the breadth of his contributions or some other meta-comment, in which case citing the editors seems appropriate anyway).

APA doesn't care whether the book title contains the author's name or not; example 21 would be same in any sort of compiled volume. Again, the APA's perspective is that the reference is for helping readers to locate the source.

So, basically, if the book is primarily written by a single author, you simply cite the book in the references section. The only mention of an editor or translator would be as follows:

Hegel, G. W. F. (1981). The Berlin phenomenology (M J. Petry, Ed. & Trans.). Boston, MA: Reidel. (Original work published ????)

As for back-to-back parentheses, the volume number and editor/translator should indeed be put into the same parentheses (with the volume, edition, titles, etc. going first), see http://blog.apastyle.org/apastyle/2012/03/citing-an-edition-of-a-book-in-apa-style.html#comment-6a01157041f4e3970b019aff8cfd3c970c

For volume numbers in titles, this is one of APA's more annoying quirks. If the volume is simply numbered, the number goes in parentheses after the title. If the volume is numbered and titled, then it should go with the title itself (because APA considers the full title of the book to be "Book Title: Vol. 4. Volume Title"). I personally refuse to store my items in Zotero in that format, given different styles' preferences for formatting of things like "Vol.", so I've resigned to not address this requirement of APA until Zotero has a "Volume title" field.

In summary, the only change that should be made to apa.csl would be to NOT include the book author in the reference when citing a book section if there is also an editor, instead just citing the editor. (To be correct, book author should never be included, instead just citing the whole book, but we can't really control that level of user behavior).

Ah, yes.

https://www.zotero.org/support/kb/italics_in_word_bibliographies