I like the flavor and aroma Maple syrup (grade B) gives to my bread.  In the Bread Bible, the water content is not listed.  Does anyone know what it is?  Also, what would the adjustment be in a bread recipe (say, cracked wheat) when substiuting maple syrup for honey?

The USDA nutrient database is great for checking things like water content:  http://www.nal.usda.gov/fnic/foodcomp/search/

As for the substitution for honey, just compare the water contents using the database and increase or decrease accordingly.  Roughly speaking, it looks as though maple syrup contains about double the water of honey.  However, I do wonder if maple syrup will have a beneficial effect on yeast acitivity the same way that honey does- you may want to increase rising times to account for that.

According to the link you provided, Maple syrup (no grade was specified on the table I found) has approximately 6.48 grams of water per tablespoon.

The other way to look at this is…
Maple syrup is primarily water and sugar. The handy Nutrition Facts label on my bottle of Grade B syrup says 1/4 cup contains 53g of sugar or 18% sugar. The remainder can be considered water.

Good point, thanks!