(The above mentioned earlier discussion on this was actually one that I started here
- so I'm glad to see this "follow-up" from a publisher who's also interested in the topic.)
I voted for putting it before the TOC as, of the three options, that was the one that would like best. However, I'm in agreement with zelda_pinwheel that it should be in the metadata - so that the reader can present it in its menu system more appropriately. So, on my Sony for instance, I would see "Continue Reading", "Begin", "End", Bookmarks", "Summary", "Table of Contents", etc., as menu items. I should be able to go directly to the summary.
I also note that when I use the "Begin" menu item on my reader, this does not take me to the table of contents and then
to page 1. Rather, the table of contents is not included in the "content" of the book pages themselves. Similarly, the summary should be a separate menu item alongside of the table of contents and outside of the normal book pages.
(So to talk about putting the summary "before the TOC" - but also then saying you don't like this because it would force you to page through it to get to the actual book - makes little sense. Because you don't have to "page through" the table of contents itself to get to the book. At least, you don't on the Sony - I can't speak to other readers.)