If anyone is building docs with bookbinder and is getting version mismatch complaints, I found this very helpful. There’s a component named haml whose default version doesn’t play nicely with middleman. Here’s the magic Gemfile entry that fixes the issue:
source 'http://rubygems.org' gem 'bookbindery' gem 'haml', '>= 4.0.5', '< 6.0'
