I'd like to say that I started reading this classic UC Gundam manga awhile back and I've just gotten back to it.
If you're watching Gundam Unicorn right now, you may want to check out this manga.
AFAIK, it has never been released in English officially but fan-translation sites like Mangathat and MangaFox have it.
Crossbone Gundam takes place in UC 179 and involves the Post-F91 universe where a band of spacepirates have unraveled a plot by the Jupiter colonies to destroy the Earth Federation.
A good mix of Captain Harlock style space-opera and Campbellian Gundam SF, CrossBone Gundam is worth the read.