They're being pricematched to iTunes. I'll do a feature post for them later when I can dig up the tie-in deals, since others in series are deep-discounted and I'm hoping this is the start of a supplementary promo pattern for PPP in addition to the hopefully-monthly direct-buy 99 cent 1st-in-series introductory offer.
by Mary Anna Evans (I'm in the middle of the 2nd in series right now and it's fun; also cheapest for $2.34 or so CAD at Books on Board, but their site is down now; may be able to match with Kobo coupons)
In the Shadow of the Glacier
by Vicki Delany (entire series is $3 or less at BoB; 2nd volume can be had for $2.34 or so, matchable with Kobo coupons)
Additionally: Wine of Violence
by Priscilla Royal (excellent and recommended, just finished reading the 2nd in series which was again quite good and fun and $2.34 or so at BoB, matchable with Kobo coupons).
ETA: Official promo via their website
(example for Wine of Violence). Given that they've removed the buy-buttons and linked to the stores, I expect this to show up in multiple venues.
And if you're willing to spend a few more cents and buy direct, they're also offering the $2.99 deals on the 2nd/3rd in series follow-ups themselves as well. Wish I'd known that before I went and splurged on some stuff at BoB earlier, but back then the promos weren't up on the site.