Desiring God has made many of John Piper’s books available for free in PDF format for many years.  In the past couple of years, in addition to his major writings, DG has also published a number of smaller works (mostly biographies) by Piper that are only available as ebooks.  These also are free.

Recently, they compiled a list of these 14 free ebooks — most of them are available in three formats:  PDF, MOBI (Kindle), and epub.  You can download them all at Desiring God.

Among the current titles are: