This Nikon D90 User's Guide Book will make you to an expert on using the Nikon D90, but this alone won’t get great pictures.
To get great photos you still need to get yourself to the right place at the right time and point the camera in the right direction, which is a lot harder than mastering the D90.
Right out of the box at default settings the D90 does a great job, but you need an eye to “see” the photos before you take them.