Learning Advanced Theme Development

Hello Everyone,
I am a web developer who has been using the WordPress platform for almost a year now. I have a working knowledge of PHP & MySQL, along with a Decent amount of HTML 5 And CSS3, I can create and customize basic Responsive WordPress themes.

What I really want to learn now is more advanced theme development that I can start releasing themes on www.remarpro.com and the like. I also want to learn how to integrate custom theme options editable through the admin interface.

Any guidance to a book or other electronic resource would be greatly appreciated.

Thanks
Zach Russell