Dan Dare, Pilot of the Future: The Biography
Not a biography of the dashing hero of the space lanes, but the story of the life of Eagle magazine and its main character. There was some stuff in there that was new, but it wasn’t as detailed as I’d hoped.
I’ve got a copy of The Man Who Drew Tomorrow, which is larger format and definitely better illustrated, but it’s been so long since I last read it that I can’t remember how it holds up on the detailed story of the comic.