Umm....I use Dev-C++ as well, and the code you posted in your very first post compiles and runs fine for me. Your book was correct. Your error is somewhere else. If you get a multiple definition error, then that's just what it is. You've probably #included the .h file more than once, therefore, it is defined/declared more than once. Here's what I have.
using namespace std;
int main(int argc, char *argv)
~SomeClass(); // Destructor declaration