Using "space" as a prefix is a cliche in science fiction. "Spaceship", "space station". "The spacelanes have been packed with spacetraders this whole space year. The space police should send some space fighters on space patrol."
From the NewsRadio episode "Space": "Your space pod is so cold and drafty." "Fine, I'll get a space heater." https://www.youtube.com/watch?v=8NDiBCD55-Y#t=10m40s
if "my space" was a brand, would they _really_ be able to forbid me to publish a book called "my space and time" based on that trademark ?
if they actually could, the world would be even sillier than previously thought. and I'd see it burn, gladly.
You can use a trademark in a title even when the book isn't about that trademarked product. There's a book titled "Amazon Warriors" which has nothing to do with Amazon. This is trademark fair use. Some trademarks create new words in order to avoid this possibility.
So no, a hypothetical "My Space" could not forbid you to write a book titled "My Space and Time". There are exceptions, like if there's a reasonable likelihood of confusion. For example, the title "My Space and Time Magazine Award Winner" is almost certainly a no-no because it implies endorsement which isn't present.