Solution to iPhoto spinning beach ball for Book projects with too many unplaced photos

Question

A few days ago I discovered the solution to this problem for a client using iPhoto 9.5.1 in OS X Mavericks 10.9.4.
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TRIED ALL KNOWN SUGGESTIONS BUT NONE HELPED
My client had already tried repairing, rebuilding etc. the iPhoto Library, and I tried OS X's Disk Verify and Repair Permissions plus emptied the cache folder in system Library and in the hidden user Library folder (option-key "Go" menu, Library). None of this helped.
CLUE TO PROBLEM
I noticed several of her iPhoto Book projects each had thousands of "unplaced" photos. In each of those cases, each Book project only had 10-50 "placed" photos used to order the book but thousands of "unplaced" photos. In a Book project, clicking on the bottom-right corner's "Photo" icon-button caused an extremely long lasting spinning beach ball making iPhoto unusable for long periods.
I discovered the problem by clicking once on an existing Book project's name in the left column of iPhoto, then letting go of the mouse with its arrow cursor hovering over the selected Book project name. Within 1-7 seconds, a little pop-up appears listing the total number of photos (placed + unplaced) in that Book project. For many Book projects, the total number was just several more photos than the number of "placed" photos, e.g., a Book with 25 photos showed "(37)" in the pop-up info by the hovering stationary mouse, meaning 37 total photos (placed + unplaced) are associated with that Book project.
BUT...
...some projects listed over 5,000 (five thousand) photos associated with a single Book project that had only placed 20-40 photos in the final printed book. One Book project had 6,070 and several other small book projects showed over 1,000 photos. In each Book project with a mass of unplaced photos, clicking the bottom-right "Photo" icon-button caused a very long-lasting spinning beach ball, almost certainly because iPhoto struggled to build a huge list of thumbnails for the mass of unplaced photos.
My client didn't understand how to efficiently add photos to a new Book project and was clicking on the pull-down menu in the right column that appears after clicking the Photo icon-button within the Book project. From the menu she chose "Last import..." or other menu choice that added a mass of "unplaced" photos to the Book project.
She didn't realize that after creating a new Book project, she could simply drag an individual photo or multi-selected group of photos or an event or "faces" group from its respective library section and drop it onto the Book project's name in the left column, thereby adding only a small group of "unplaced" photos.
USER SOLUTIONS
=====Delete mass of "unplaced photos" within a Book project
This works best for cleaning up smaller number of unplaced photos from completed Book projects.
Problems with solution:
- if the number of unplaced photos is huge, e.g., 6,070, the list of unplaced photos won't appear for a long, long time if ever.
- even if the list of unplaced photos finally appears, there's no way to select more than one thumbnail at a time, i.e., command-a for Select All doesn't work, nor do shift-clicks and command-clicks for multi-item selecting. You must click one photo then tap the "delete" key on your keyboard repeatedly and fast for this to be practical (note: delete key presses are cached here (meaning accumulated until it catches up processing them later); tapping the delete key like mad then waiting for iPhoto to catch up takes lots of patience.
====Delete an entire existing Book project containing a mass association of unplaced photos
This is practical if you've already printed your Book project and no longer need it. My client chose this method for Book projects with a mega mass of unplaced photos.
Problem with solution:
- for incomplete Book projects in progress with a mass of unplaced photos, you'd have to start over after deleting the whole thing.
NEED FOR IMPROVED IPHOTO FEATURE(S)
(1) The existing "Clear Placed Photos" button within a Book project might be useful, but it'd be even better to also have a button to "Clear Unplaced Photos,” and this button should be available outside of the section that struggles to display thumbnails of large numbers of unplaced photos. Clicking "Clear Unplaced Photos" would do the trick.
(2) An additional iPhoto behavior might help: iPhoto should warn with an option to cancel when adding a mass of photos to the "unplaced photo" section if the number of photos exceeds ??? (400??).
(3) Add another choice to iPhoto’s special startup Administrative window (Repair, Rebuild, etc.): "Remove unplaced photos from existing projects. (Doesn't destroy any photos in Library)"
Whew!

Answer 1

Like I mentioned in the post, corruption was probably ruled out by running all the Admin features at iPhoto startup (e.g., Rebuild, etc.). I also stated in my post that I also ran a Disk Verify and Repaired Permissions in OSX (via Disk Utility). I also emptied system Library cache files as I stated in my post.
I was paid to figure out the solution and am not getting paid to troubleshoot for Apple. The more unplaced photos there are in a Book project, the longer it takes to build thumbnails. It's an old general problem in computing when building lists on the fly.
The delay happened for all Book projects with lots of unplaced photos (almost*** certainly more than Apple imagined a user would use), and the beach ball delay was proportional to the number unplaced photos, which super large numbers of photos.
I very much doubt photos are corrupt. But Apple will probably figure it out. It was EASILY reproducible. Try it with different number of unplaced photos known not be corrupt (they display fine elsewhere and iPhoto's and Disk Utlity's admin Verify, Repair etc features show no problems).
I'm done with this.
My client's iPhoto works well now and she knows how avoid placing exorbitant numbers of unplaced photos into her project. I'm not getting paid to answer all this, so good night.
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***"Science is the outcome of being prepared to live without certainty and therefore a mark of maturity. It embraces doubt and loose ends."
  — A. C. Grayling