ABANDONED. A book about an astronaut that goes into space and finds a galaxy made of the dark matter/anti matter

[Lex]

Hi guys!
So the title pretty much sums it up, I'm looking for a book about an astronaut from Earth that goes into space and finds a galaxy made of dark matter/anti matter where he meets a girl made of antimatter.
I don't know when this was published, I guess it goes in the sci fi genre and I don't really know anything else about the book seeing as I only heard this and have no way of asking the person I heard it from.
So thank you if anyone knows the title xoxo

[Lobstergirl, au gratin]

Does it involve romance with the girl made of antimatter?

[Kris]

Lex, what year did you hear about this book?

[Lobstergirl, au gratin]

Lex, are you still looking for this or did you find it?

[Lobstergirl, au gratin]

No response, moving to Abandoned.