BASIC Primer for the Commodore 64 by the NorthWest group of California - Although this is titled as an introduction to BASIC programming, it doesn't lean towards the technical side of things.  I would consider this more of an introduction to the Commodore 64 and the 1541 Disk Drive along with some commands you would use from BASIC to control your computer.

This archive includes the full NorthWest Starter Kit.  There are some other utilities / programs you might find useful on it.