I'm using the new SItepoint ruby book. On page 100, it says to start the script/console. When I try to do so, I get this error:

Loading development environment.
/usr/lib/ruby/1.8/irb/completion.rb:10:in `require': No such file to load -- readline (LoadError)
from /usr/lib/ruby/1.8/irb/completion.rb:10
from /usr/lib/ruby/1.8/irb/init.rb:218:in `require'
from /usr/lib/ruby/1.8/irb/init.rb:218:in `load_modules'
from /usr/lib/ruby/1.8/irb/init.rb:216:in `each'
from /usr/lib/ruby/1.8/irb/init.rb:216:in `load_modules'
from /usr/lib/ruby/1.8/irb/init.rb:21:in `setup'
from /usr/lib/ruby/1.8/irb.rb:54:in `start'
from /usr/bin/irb:13

Any ideas? Thanks.