It's a simple concept: what if Luke and Leia had grown up with their Dad...?
And it's proved to be a massive success. It's all done with the affectionate charm that has served creator Jeffrey Brown well through his confessional comics days. Kids love them because they're cute & parents love them because it mixes parental-truisms with beloved lines from the original series. Darth Vader and Son (see here) is now the followed-up with Vader's Little Princess (both from Chronicle Books).