I started reading this book series around 2000 from the school library and changed schools before finishing. I believe it was a series, possibly a trilogy, told from both the humans and the aliens perspectives. The human star fighter pilots would link minds in the fighters to fly better and the alien ships were made of ceramic materials that seemed to make them impenetrable. Also, the aliens’ ancestors would continue existing as ghost like entities to advise the following generations.
This is Timothy Zahn's Conquerors trilogy. The first novel is from the point of view of the humans, particularly Cavanaugh when they first encounter the aliens whose ceramic ships are nearly indestructible to the humans weapons.
The fighter pilots are called "Copperheads" and while effective there's a problem because use of the interface is addictive.
The aliens (Zhirrzh) are the viewpoint characters for the second book. When they die an organ is extracted from their spines from which their consciousness can still manifest. By dividing the fsssk they can appear in 2 different places and act as a faster-than-light communication system.