I just noticed that over at Amazon.com Robert Gundry’s Mark Commentary is available free as an eBook for kindle. Note, this is not his Mark: A Commentary on His Apology for the Cross (1993) , but is a chapter from his one volume Commentary on the New Testament (2011). It is a good little read. I think Gundry cracked Mark as an apology for the cross. The more I read the Gospel of Mark, the more I think Gundry is right. His big commentary on Mark is easily in my top 3 Mark commentaries, and this free ebook is a useful digest of his exposition of the Gospel of Mark.