The title in the metadata or the filename? Keep in mind some readers don't use metadata and just guestimate author and titles from the filename.
Filenames need some characters removed because they're 'reserved' in some operating systems (you want to at least be compatible with Windows, MacOS and Linux)... the plus (+) sign being quite a common operator, it might not be allowed in one or more of those file systems.
Hey, you've got books on C++, they OUGHT to speak a bit about namespace management...
