Yeah that's looking more like a puffball to me, however I've never had experience with them so I will defer to others on this one. Save it though, it might still be something you can use and some mushrooms can last for up to a week in the fridge (but maybe put it in a paper bag -- if it IS a puffball you don't want it exploding spores everywhere).

Oh, just for future reference, when you are dealing with look-alike mushrooms one of the first things you want to check is for gills under the cap (although I don't think you'll ever see them of puffballs?). The type and color of gills are very important in identification, so take as close-up a shot as you can, then a bit further away to get the underside of the cap. Along with your images of the top of the cap, and view of the stem, that will nearly always help to positively identify a mushroom. Unfortunately some are so close that the only way to be sure is to get a spore print and see what color the spores are. I have one growing in my yard where white or yellow spore prints are delicious, but green is deadly. Mine are delicious. :-)