Ask Mr. Smarty Plants

There really aren't any books that address this issue for your area specifically, but there are a couple of things to consider when planting on a slope.

The most obvious is the daily and seasonal differences in light exposure (and thus air and soil temperatures) on the north and south sides.  So the plant communities on the south side will be adapted to sunnier, warmer conditions (and a longer growing season) than on the north.  The other thing to consider is drainage.  Both water and cool air (and sometimes soil and nutrients) flow freely downhill resulting in tough and often dry growing conditions.  That is why you often see plants thriving on a hillside wedged in a crack or between a couple of rocks.  That is where water runs to and collects and organic matter a gets trapped, providing nutrients for the plant. Once a plant gains a foothold it can sustain itself by improving the soil conditions within its root zone. 

In order to find a listing of plants that would be adapted to hillside conditions you can visit our Native Plant Database.  If you do a Combination Search for Wisconsin and select dry soil conditions you can create lists of plants of differents types for the north and south sides.  Each plant name on the lists is linked to a detailed information page with images. Plants with fibrous root systems, like grasses and plants that spread by stolons do well on hillsides and help prevent erosion.

An internet search for hillside plant communities produces a number of articles on your subject and there is an interesting Q & A article on the Kenosha extension service website  that you might find helpful.