There seem to be so many eBooks, forums and blogs on the subject of Adsense that I wonder if there is anything left to learn. Do you have any burning questions you can't find the answers to? T
You have to understand that there are always people "Just starting out" To them its all questions...That is who most of these books are being marketed too. For experienced users, nothing beats getting real time advice in forums such as this. It was a DP member that started (or at least took it to the next level) placing images next to ads. By the time an eBook sold the idea, the CTR had already dropped Nothing beats forums for info these days
Most of my sites are doing fairly well in adsense, while others could be doing a lot better. I can't really think of anything else left to learn about Adsense. Adsense is pretty straight forward. The biggest challenge for me personally is affiliate programs. I have a lot of questions about those, even though this is the wrong section.
The only thing I would stress is ad placement.It must be placed in a spot where people will click and must fit into your site and look natural.
There will always be something to learn because Google is always making changes to the AdSense program. Change is the only constant.
There is always something to learn. Even if you change something on your site and get a lower ctr you've learnt something.