In the "Cancerverse", Mar-Vell did not submit to death, but instead made a deal with the Elder Gods for eternal life. I really like the idea of the villain being a hero who was trying to do good, but has had their ideas corrupted, but this is lost in the art of the comic, with the Cancerverse heroes appearing demonic and twisted compared to their 616 counterparts. There's also a major battle between the Celestials and Elder things of the Cancerverse, which is not shown, but is described by Silver Surfer as taking place on a plane of reality that mortals cannot comprehend. Odd, the same kind of battle was shown in The Galactus Seed pretty neatly. By far the best moment in the comic is the assembly of the Annihilators (shown above), a team consisting of Quasar, Beta Ray Bill, Gladiator, Nova, Silver Surfer and Ronan that plan to fight their way into the Cancerverse and take out Mar-Vell. This plan doesn't work and we barely get to see them fight.
The core concept of the story is that only death can defeat life, hence the need to get Thanos to Mar-Vell. This idea that Thanos keeps coming back to life to bring balance to death is ok, but we've already seen it done, and done better, with Galactus. The Thanos Imperative is not the epic that Annihilation was, but still has its moments and a few epic set pieces. If you're keen on more Marvel space stuff and have read all of the Jim Starlin bronze age stuff, this is probably worth your time. Not much like the Guardians of the Galaxy films though, if that was what you were looking for.