Really interesting points. I didn't know about the Heinlein book but it must have had a very powerful effect at the time it was written. I also hadn't considered that this may be why so many films of books disappoint. I have sometimes watched the film first and then read the book . After seeing The Eagle has Landed, I could only ever see Donald Sutherland as Liam Devlin. But from the comments so far, readers do seem to like a rough idea of physical appearance - but not every last detail of clothes, etc. Thanks for your help!