Can FREE Promotions Help Indie Authors?

October Promotion of A Tale of Two Colonies:

Giant creepy crawlies, including spiders, attack in this adventure and romance story set on The Planet of the Giant Arthropods, aka Delta, after a local airline (excuse my wild imagination). This story seemed suitable for a Halloween promotion.
The eBook is only 99c until November 1st:
http://www.amazon.com/dp/B00MFY8A5Q 

As an Indie author, I appreciate free promotion. But, how well does it work? In September, I ran a small paid promotion on another book and essentially broke even after a week. This month, I tested a different strategy on a stand-alone book.  Using free sites only, I promoted the ebook FREE from Oct 16-20^th and then at 99c for the rest of the month.

Crude unscientific summary: 
The book hit #1 FREE in Colonization and Space Exploration subcategories on Amazon and I gained a few sales and kindle unlimited reads over the next week or two. 

Would I do it again? Yes! This free promotion worked better than the paid one I ran in September on another book and the book achieved temporary prominence after weeks of inaction. 
  
Here are the results:

eBook FREE for Oct 16-20 

A total of 1796 copies given away.

Listed on the following sites:

http://www.indiebooklounge.com/

http://askdavid.com/free-ebook-promotion

http://bookdealsdaily.com/promote/

http://theereadercafe.com/promote-your-books/

http://eBookLister.net

http://kindlebookpromos.luckycinda.com/

http://www.armadilloebooks.com/submit-free-ebooks/

http://bookdealhunter.com/submit-free-book/

http://www.freebooksy.com/editorial-submissions/ 

http://www.frugal-freebies.com/p/submit-freebie.html

http://indiebookoftheday.com/authors/sponsorships/

Top rank reached on Oct 19^th

Amazon Best Sellers Rank: #134 Free in Kindle Store

#1 in Kindle Store > Kindle eBooks > Science Fiction & Fantasy > Science Fiction > Colonization

#1 in Kindle Store > Kindle eBooks > Science Fiction & Fantasy > Science Fiction > Space Exploration

I'm pleased with this rank since I have never achieved a rank of #1 in previous promotions.

eBook discounted to 99c from Oct 21-31

by 29th – 14 sold + a few thousand reads. Not spectacular, but better than the book did in the month before.

Submitted to the following sites:

http://bookpraiser.com

http://bookscream.com

http://bookdealsdaily.com/promote/

http://www.indiebooklounge.com/

http://readfree.ly

Top rank on Oct 23th

Amazon Best Sellers Rank: #19,461 Paid in Kindle Store

#142 in Kindle Store > Kindle eBooks > Science Fiction & Fantasy > Science Fiction > Colonization

#143 in Books > Science Fiction & Fantasy > Science Fiction > Colonization

#152 in Kindle Store > Kindle eBooks > Science Fiction & Fantasy > Science Fiction > Space Exploration

Secret Weapons
I acknowledge help with tweets and retweets from the members of the eNovelAuthorsatWork group and a catchier book description created with advice from Bryan Cullen’s FB group Selling for Authors.

My thoughts:

Free promotion can work if you have a good “street team” for sharing.

The boost is temporary.

Discounting to 99c helps to track the results and brings in more readers. 
What strategy works for you?