@Katro No the 1.3 book is the last out there. However for 1.4 this thread gives good information on how files/folders are structured now. You will still have very good use of the books though. http://www.magentocommerce.com/boards/viewthread/77585/
@WebinCode You need at least change the toolbar file. Read the release information to be exact where. If nothing is happing maybe your are just lucky?
Correct. I already tweeted Themeforest about this can be misleading to consumers. From a customer point of view when a theme is compatible with version 1.4 this does not mean it is build from the ground up on the new structure. To make a theme compatible you only need to change one file.
Al currently available themes on Themeforest (and Magento Connect) only are compatible and not taking advantage of the vast improvement of the new structure and SEO changes.
Magento has a good starting theme “the blank” theme to get developers started: http://www.magentocommerce.com/magento-connect/Magento+Core/extension/518/blank-theme
An alternative is this one from Yoast: http://www.magentocommerce.com/magento-connect/Yoast/extension/974/yoast-blank-seo-theme
This could have several reasons. I would encourage you and other authors to look into the extensive Magento Forum as I’m positive your answer will be there. You can also start here (via themeforest twitter account) http://net.tutsplus.com/tutorials/php/magento-for-designers-part-i/