Daniel Schinhofen let us know that he is publishing the 4th book in the Apocalypse Gate series on May 15th and to help promote that, he plans to put all the earlier novels on sale. The sales will be staggered a little with the biggest discounts happening early starting at $0.99 per book and then gradually rising till its the normal price. So, buy early folks.
Book 1 - Sale from May 6th-8th
Book 2 - Sale from May 9th-11th
Book 3 - Sale from May 12th-14th