Interesting assortment, but quite a few items are out of date, and there's nothing to indicate quality. For example, I took a look at the online "Ruby Essentia

Interesting assortment, but quite a few items are out of date, and there's nothing to indicate quality. For example, I took a look at the online "Ruby Essentials". Horrible. The section n variables is just wrong, and will leave people extremely puzzled about program behavior.