Mycroft is secretly a very prolific children's author writing under a pseudonym.

Bonus from re-reprompter:
- Sherlock secretly ADORES the books because sentiment They remind him the stories his brother told him before their relationship became sour.
- Mycroft dedicates the books to "Will" for some angsty reason.... maybe for not being there when "Will" needed him...
- Neither of them know about the other's association with the books

Original Reprompt: http://sherlockbbc-fic.livejournal.com/16422.html?thread=96071718#t96071718