Anyone thinking of using interface classes like the ones described on page 49 (which is a very good idea by the way) should remember to include a virtual destructor in the interface declaration. Otherwise, deleting the derived class through an interface base pointer would fail to call the derived classes destructor (and after all, interface classes are designed to be accessed through an interface base pointer).

This isn't really an errata, I think the source code includes this. But it isn't included in the example on page 49 and it can cause serious headaches so I thought I'd mention it :))