We have introduced the ERG in CERT training.
Below are a few different ways you can get a version of it.
you can download the pdf at http://www.phmsa.dot.gov/staticfiles/PHMSA/DownloadableFiles/Files/erg20...
There is an app you can purchase at http://everydayemstips.com/emergency-response-guide-apps/ or other sources
you can also order an actual book from a variety of sources. Google Shopping is a great source to find one.
What ever form you choose it is a good resource to have.
If you have other options feel free to post them in the comments.