I read these 3 books from the Alien and Predator universe, and LOVED them. They are:
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Predator: Incursion
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Alien: Invasion
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Alien vs. Predator: Armageddon
All written by Tim Lebbon, they create the Rage War trilogy. He does a great job of character and universe immersion. I wanted to let everyone know: the titles of the books make it seem like the major plot revolves around Aliens and Predators fighting each other, but the majority of characters are humans. We get in depth looks at Weyland-Yutani higher ups, the Colonial Marines, and lots of hardcore sci-fi and creative new technologies.