Hi,
It's difficult to gauge to give advice as 'beginner' could be many different levels...........
I assume you have started to use Excel for work and wish to learn more? If so, one approach is everytime you come across a problem, start researching what the best method is to resolve that problem............I always find learning much easier when you are learning a solution to a problem, as opposed to reading something from a book when you can't really apply it.........
This forum is an excellent source of information and a way to learn. Just reading up on peoples issues and the solutions that users supply can go a long way to helping to increase knowledge.
With regards to books, I'd have a look on Amazon or something........There are hundreds(Thousands even?) of Excel books out there, so reading up on the reviews will ensure that you pick a correct book for your knowledge level etc.
Good luck!