Old Man's War by John Scalzi - incredibly readable, fun, spacey sci fi https://www.amazon.com/Old-Mans-War-Book-1-ebook/dp/B00AZRP2GA/

The Passage by Justin Cronin - super readable also, gripping & immersive https://www.amazon.com/Passage-Trilogy-Book-ebook/dp/B003TJA8Y2/