I even visited your site to check it out. In your case, you have your own book to sell thus more options to make money. If it was a niche, I would only had Adsense on it. Like you, my site use more than Adsense since it’s not a niche.

Here a few pointers:

First, you should watch this video:
http://www.viddler.com/explore/bloggerunleashe/videos/47

Second, since I clicked from this post, I saw your Adsense ads. You should only show your ads to search engines. I made the switch myself recently and I increased my Adsense revenue by 64%.

Third, your could switch to free/low cost alternative. I had to mentioned it

Since it’s been 2 years and make money, you should no longer have a need for SBI. But, if you still want to stay with them at this time to play “safe”, you could start another site(niche) on your own and learn from it. It could be a sub niche in the fashion field. Later, when you feel confident, you could leave SBI or not.

The last recommendation goes to those that did not go beyond the world of SBI. Just use a sub niche of your main SBI site using alternatives to the SBI tools. In any case, you will learn to be more independent.

have fun!