Thought I'd put up another book recommendation entry.
Drawing: Space, Form, & Expression is a really good book that helps to expand your artis's creativity. It quickly runs through the basics but doesn't babysit you. It just tells you simply to draw and the general approaches and then let's you explore.
Too many drawing books are overly simplified tutorials that want to break down every stuff of drawing every object. While those books have their place, this one gives you the approach to being the one to discover how to create these things on your own. Learn how to view the world and you can pretty much draw everything. There are lots of excercises to help you explore the space on your paper and it's really just fun to go through. There are some great excercises about drawing from your imagination and turning it into something tangible
The book ends with a portfolio of contemporary and student drawings that explore the principles that you've learned throughout the text. Definitely one to check out, read through and follow.