This thick trade paperback reprints the Batman/Alien comics from the 90's. In Batman/Aliens, Batman is in South America and crosses paths with a military government group. The come across a crashed spaceship in the Amazon jungle and find dead aliens with their chests exploded. There are also the open ALIEN eggs all about. Soon, soldiers begin disappearing to be found later with the creatures inside them. Full grown aliens appear and everyone is killed except Batman and the woman leader, who turns out to be working for a secret organization. She wants to use the Aliens as a biological weapon and Batman now has to stop her. The coolest thing about this story is when an Alien crosses with a crocodile and we have this Alien/Crocodile Hybrid.
In the next story, BATMAN/ALIENS II, the Aliens have come to Gotham. The story begins in Antarctica in 1928, where a group of scientists have discovered the Aliens deep beneath the ice. And one of those scientists had survived and the alien he transported is awakened after all these years. Batman knows what a dire threat these creatures pose to humanity and tries to stop them. What he finds out is that they're being used to create weapons at Arkham Asylum and it's there he has to fight Alien/Super Villain hybrids created from the Joker, Mr Freeze, Two Face and Poison Ivy. It sounds sort of silly but it works quite well.
Then, there's the SUPERMAN and BATMAN vs. ALIENS AND PREDATOR, which I didn't find quite as entertaining. They encounter a colony of Predators that have been isolated deep in the Earth for a while and Batman defeats the leader while wearing his Bat-Armor. Earthquakes are destroying their home-and Batman and Superman try to find a peaceful solution while The Earth's Terrestrial Defense Initiative wants to blow them all up.
I haven't read these stories since they came out and they hold up well. Recommended.