There has been a lot of the free smaller versions of the “For Dummies” books published recently. These are normally sponsored by a company to help promote a way of thinking/product/etc, however they do contain useful overviews and information on the subject that they are presenting on.
Here are my top 8 of these which should be on your reading list for the start of 2016. All are downloadable in PDF format*.
*You may need to sign up to receive some of these books.