Shawl patterns are usually very adaptable to different weights of yarn. The shawl as pictured in the book looks quite small, almost like a shawlette so if you wanted a larger, full sized shawl, using a heavier weight yarn would be the way to go. Remember if you use a heavier yarn to increase the needle to about 2 sizes larger than what the yarn label recommends. This is necessary to get the proper drape.
Light shades tend to emphasize lace patterns more although you can find some very striking looking lace shawls done in dark shades also. If you haven't done much lace work you will find lighter colored yarns easier to see.
Regular mohairs usually do not show lace patterns well because of the halo. However, lace mohairs like Kidsilk Haze, Kid Seta, Douceur et Soie, etc. can be used very effectively in lace.