These books are great fun for kids. There's really nothing like them today that makes reading fun for 8 to 10 year olds.
Also appreciated is the fact that these were stories firstly, not just product. Yes, it involves popular characters, but it's not merely a novelization of a tv show episode. These are original stories.
And thus, there are differences. Brutus is named "Larder" in this one, but he looks and acts like Brutus, so that's fine. And Popeye has no speech impediment, employing perfect diction.
But the author get things right. Olive's character is distinctly Olive, and the Sea Hag is perfect. And Popeye saves the day in true fighting sailor fashion.