Keep iTunes library in sync on OS X and Boot Camp (Windows 8)?
Later edit
See iTunes: Moving iTunes Files (Self Managed) for a better explanation of how to achieve dual, almost-in-sync libraries across different machines 



[This is not a hugely technical explanation, more one of the frustration I've had doing the same thing... if you want more details, ask...]

You can share the file location, but both machines will 'see' it differently. iTunes uses absolute references [truly irritatingly] so the only way to keep the Library in sync is to either add the same files to both [not good if it's supposed to be self-organising] or to manually copy the iTunes Library.xml file &amp; use BBEdit to change the path structure for every entry - which can be done but then may take the Windows version of iTunes up to 10 hours to process it.