I'd been hunting for this book for my collection for some time. It's one of the comics from my childhood that made an exceptionally big impression on me. I think it was just the cool-looking monsters on the cover and the striking colors used here. This is a cover that grabbed me and left its image imprinted there forever on me old brain.
I used to think that it was a Ditko cover, but the figures of the people are obviously by Jack Kirby. So over the years I finally figured that it must have been penciled by Kirby, or perhaps he laid down some rough layouts and Ditko finished it up. But the inking is definitely all Ditko. There are a few examples over the early years of Marvel where Ditko went in and inked over Kirby's pencils. Not often, but it did happen from time to time. Steve Ditko is one of those artists whose style is overpowering, so his inks tend to hide the original pencil work to a great extent.
Anyway, I have my copy, now.