SOLVED. Fiction/Dramatic. Mind experiments take academic to another world in her head.

[Sarah]

A university staff member, becomes involved in an experiment with her neighbor, possibly with drugs, where they go to another word in their minds temporarily. But they stay longer each time.
They have to do something dangerous in the other world, and then decide to stay - maybe ending up catatonic in the real world. Possibly written 8 years ago. Set in modern times, I think in the UK. Cannot recall author

[Sarah]

Maybe the woman's boss got stuck in the other world in his mind, and she find his experiment among his academic papers. I feel like it had the word magic or magician in the title?

[Lobstergirl, au gratin]

Sarah, please add genre to your topic header. Is this fiction or nonfiction? Fantasy?

Dramatic or comedic?
Author's gender?
Cover?
Where and when is it set?

[Sarah]

It came to me in the end - it was The End of Mr. Y