You can learn theoretically about the tools ans their usage. But when it comes to practicality, you must practice the theory then only you can master it. Try checking Youtube and some other tutorial sites which can provide Video tutorials. All the best to your interest.
By the way, I just found this link here on DP. Hope it might help you. http://forums.digitalpoint.com/showthread.php?t=2400499
Hello Delwar, Generally, you can learn PhotoShop by using an eBook. However, keep in mind that you will only learn what the provided tools are used for. If you actually want to be a designer, you will have to practice by creating graphics / web pages in PhotoShop as well. A lot. If you'd like, you may add me on Skype so I can help you directly.