Saw this at the comic shop today and looked through it. It's divided into three stories. What if the Hulk died? What if he landed on the planet they sent him to? and What if Banner arrived on Sakaar?
For the first story my initial thoughts were: "This is the way WWH should have been done!" By that I mean Caira's lightning quick strike to take down Earth's heroes before they had a chance to form a defense or even know what they were up against.
The defeat of Black Bolt is again left off panel so we have no clue what happened other than a big chunk of the moon was blown off. We have no clue as to how that happened.
The death of the Sentry makes some sense because he did not have a chance to power-up and Black Bolt hit him with a very powerful attack.
The only thing is once again the Avengers fell too easily, but considering the whole story had to be told in about ten pages I can give it some leeway.
We off course get the obligated conclusion where Caira joins the Hulk forever.
Would Earth's heroes have fallen so easily? It is a What If? So pretty much anything goes. What made me like it better than WWH main is the attack was quick enough that Earth's heroes could be taken out before they had time to prepare instead of the warning the Earth's heroes got from the Hulk, twenty-four hours to prepare, and failing so miserable.
As to the second story: It was well done. Turns out in the long run both Hulk and Banner would have been happier if they had not gone to Sakaar. It does raise a question about the Hulk's age. But being a What If? that point is largely irrelevant.
The third story is a one page comedy that is a nice end.
Overall I enjoyed this better than the main series: