I'm not familiar with that guide in particular, but in general guides with drawings are better for most purposes. The best is undoubtedly the Sibley Guide to Eastern North America. All the drawings are in the same pose which really allows you to pick out the differences between species. I suspect your guide is not doing that very well, as most gulls have a white head, pink legs and a yellow bill with red spot.
If you prefer a guide with photos the Kaufman guide is probably the best, as it does a good job of showing birds in similar poses and pointing out what the differences are.