This is interesting.
Smashwords owner Mark Coker recommends a free pilot sequel to a series. So, Solar Wind 1 is up there for free, until a certain amount of downloads have been achieved (my personal experiment, see?). And the glossary is up there perma-free because it is an add-on that is - while not really necessary, handy to have.
Then, he has an option "reader sets price". This means of course that the reader can decide the book must be free.
Thirdly, right now there is a promotion where one can get up to 100% "discount" on a book "purchase" (meaning, it's free once more). There are other options too, e.g. 75% discount, 50% and 25%.
So for savvy readers, the entire series is momentarily up there for free!!
1. The Mystery of the Solar Wind: Free until a certain number of downloads (my experiment).
2. The Assassin: Reader sets price.
3. Freedom Fighter: On promo with 100% discount.
4. Raider: Ditto.
The Morrigan (Solar Wind 5) is sadly not up yet, I'm formatting it right now, it will not be in time for the promo which ends in 2 days; but as for the first 4 books, grab your copy while they are up there for free!! And if you then actually read them, and you like them - show the Solar Wind's crew your love and tell a friend or two! :-)