I would also like to add that although TAB is ok if you already know what the song sounds like, it doesn't help mush if you have never heard the piece of music you are trying to learn. This is where standard notation comes in. I know it seems intimidating at first but everything you need to know about a piece of music can be described with standard notation. I mean we are talking about pitch, position, tuning, rhythm, tempo, dynamics..etc..etc.. Even the overall emotion of the piece can be described in notation.
In my opinion, the most difficult part of learning to read music is making the connection between what you are reading and physically relating it to your instrument in an efficient manner.
I would like to recommend a couple of books that helped me out a lot. The first is by Vince Bredice, a jazz teacher who worked with Jaco when he was teaching at the University of Miami many years ago.http://books.google.com/books?id=b5SWtW-yW_AC&lpg=PP1&ots=4aozaHQtrS&dq=Deluxe%20Jazz%20%26%20Rock%20Bass%20Method&pg=PP1
The next is a little more involved of a book but it really helps to develop the "hearing eye" for reading music. It is by Paul Hindemith - Elementary training for musicianshttp://www.amazon.com/Elementary-Training-Musicians-Paul-Hindemith/dp/0901938165
Fortunately we have the internet, a source of infinite amounts of information at the click of a button. But there are still some great books out there that provide an excellent point of reference.