Sketching textbook?

[Geo Dude]

I know many people here have an interest in the arts outside of writing, so I thought I'd pose the question at this board:

Does anyone know of a sketching textbook (or something along those lines) they can recommend me? Preferably something that starts at basic level and moves to more advanced material and can be found used for cheap on the Amazon marketplace. I'm looking for something a bit more substantial than 'here's an object, draw it!' Ideally it will be something that is written at an adult level with instructions on how to improve one's technique along with examples.

For a bit of background: I'm a geology major that's currently out of college and geology tends to be a sketch-heavy field. I've decided that while I'm out of college I'll focus on improving areas where my skills are sub-par rather than just assuming I have no natural talent and will always suck at those things like I have in the past. Sketching happens to be one of these areas.

[bhodges]

This book is excellent, Drawing on the Right Side of the Brain, by Betty Edwards. (I used one of the earlier editions in college.)

You can buy it on Amazon below, and they also (of course) now have a website. In a nutshell, her approach is to train you to see what's actually there when you're looking at something (a model, a landscape, a still life, etc.), rather than what you think is there, and her techniques - many of which are quite fun - are good for people of any level.

http://www.drawright.com/

http://www.amazon.com/The-Drawing-Right-Side-Brain/dp/0874774241

[asin]0874774241[/asin]

--Bruce

[Geo Dude]

Thank you.  A secondary goal was to improve my sketching skills not just by improving my sketching technique itself (straight lines, shading, etc.) but by elevating my understanding of how to draw objects.  This book seems to fit that bill perfectly and is available for cheap!