Infernal Devices begins as any solid next book in a series should. (goodreads.com)
There are a few sets but if you want one of the single covers turned into a set it will be a normal next book in a series custom order — more info on the custom cover design page. (bookcoverscre8tive.com)
The next book in the series, The Gentle Parent: Positive, Practical, Effective Discipline is due to be released November 2013. (kerenthrelfall.com)