'The ending makes the movie'

... so I'm reading Maltin's book and the review for this movie says 'The ending makes the movie'. Perhaps I'm missing something, but I thought the ending added nothing to the movie. I'm assuming he's referring to the scenes at the asylum/rest home with Jason in the wheelchair. What difference does it make if he imagined the whole thing? Or if it really happens and no one believes him? Am I supposed to believe that the sight of mirrors drives him into a suicidal frenzy? If it was supposed to have a Twilight Zone -esque 'twist' then it wasn't executed well. I just didn't get the shock and found those scenes superfluous, much like all the damned explosions.

To me, the interesting parts of the movie were the exploration of the idea that this other planet could exist.

I also liked it when they dissected the body and found the organs on the wrong side of the body. I hadn't thought of that.

The preparation for liftoff montage was interesting even though it was a little slow.

I liked all the miniature work - it was very nostalgic. I thought they even did a passable job of simulating weightlessness in space. Clearly they didn't have a 'vomit comet', but, hey, moving in slow motion while attached to a wire can work just as well!

I found the psychedelic effects to be a bit pretentious - just seemed like a cheap attempt to cash in on Kubrick and class up what is essentially a B movie.

In the end, I liked the movie for what it was even though I was distracted by its poorly executed efforts to be something else.