In general, I'm not a huge fan of work books. I think in most cases there are better ways for children to learn and practice their skills.
Carter is a smart barely four year old that has pretty much given up napping in the afternoon. So afternoon time has become quiet time and I've tried to find activities that he can do that need very little parental involvement, but challenge him mentally. I'd love to set up fun, creative activities for him every day, but frankly, I don't have the time for the energy to do that. The SCHOLASTIC SUCCESS W/ KINDERGARTEN book has been a lifesaver for me. It has a variety of different activities, including numbers, letters, opposites, and more. Some of it is a little too advanced for Carter at this point since his reading skills are still limited, but I bet he'll be ready for them soon. And Carter must be enjoying them because he keeps asking to do more.