Hello,
Can anyone know why magento does not provide any manual or developer guide? All most all framework and CMS provides their official development manual But in the case of magento I did not found any official manual which is very surprising thing.
Learning magento is hard because they are making this thing hard.
Thanks
The best resource you will find is Alan Storm's blog and he has recently written an oustanding series on the Knowledge Base called "Magento for Developers". Both of those will give you exactly what you are asking for in terms of customizing Magento. First, you must know the framework, then you can understand how to customize and extend it. Otherwise you are just hacking.