With effect from a couple of days ago, if you buy the Viridian System Sampler at Smashwords (for 99c), your copy will include a link to the forthcoming Perihelix, together with a coupon code.
When you buy The Perihelix after it is released on February 16th, use the coupon and get your money back on the Sampler. That means your Sampler was free. Or you got two books for the price of one. Or something.
The coupon ends at the end of April. The Perihelix price may change at the end of March, but it will definitely change by the end of April. It’s called promotional pricing, so it depends how long it takes the promotion to work!
If you have already bought the Sampler, check back at your buying site for the new edition, it should be updated free.