what is the best bread cookbook for beginners?

In addition to the ones Stephanie B mentioned, I would go for any of these 2, both for guidance and good recipes that will stay with you:
Beard in bread
Bernard Clayton's new complete book of breads

I like Peter Reinhart's Bread Baker's Apprentice, or Rose Levy Beranbaum's Bread Bible. Both have a variety of recipes, good explanation of steps, and good photos/illustrations.