The Discipline Book, by William and Martha Sears is a great reference book for all kinds of discipline issues.
Their discussion on spanking in particular made me feel much better about my choice to spank in the past, and encouraged me to explore different (better) disciplining techniques in the future. Their explanations for and against various punishments were not as concrete as Unconditional Parenting, so it helped me feel less guilty as a parent, but Unconditional Parenting was so polarized to one side, it motivated me more to see things completely differently. I am glad I read them around the same time, to compare and contrast methods.
The Sears brought up issues that I had thought a lot about, but didn't know an expert would point out. Phoebe is a twitcher and a tooth grinder, and there was a whole section on how to squelch this behavior. I am not sure if their techniques will work on her, but that validated my concern for her twitches. Mostly I am watching her overall anxiety levels and trying to find correlation between events in her life and her twitching. I am worried less about it now, knowing that a lot of kids behave in this way.
I saw on the back of the book that there are a ton of Sears books out there, so I am curious as to whether or not the material overlaps. I think for a used copy at 1 penny on amazon, it's a nice reference book to have on the shelf in a bind.