Authentic

"Mark 16:9-20 is not in many of the oldest and most reliable manuscripts."
"Mark 16:9-20 is not found in any manuscript until the 800s."
"Mark 16:9-20 was added over two centuries after the Gospel of Mark began to circulate."
"Clement of Alexandria and Origen affirm that the Gospel of Mark ended at 16:8."

Those statements are all false.

In this book (now in its fourth edition) James Edward Snapp Jr. identifies some of the individuals who have misled American and European readers, students, and congregations about Mark 16:9-20 - twelve verses of sacred Scripture. He also demonstrates the numerous errors committed by authors such as James R White, John MacArthur, Craig Evans, James Edwards, N. T. Wright, Norman Geisler, Bart D. Ehrman and the late Bruce Manning Metzger.
For far too long, vague and poorly worded footnotes have caused millions of Christians to doubt whether Mark 16:9-20 is inspired and canonical Scripture.
Brother Snapp sets the question of motive to one side, and focuses directly on the evidence found in Greek manuscripts, church writings, and more. In the opening summary-chapter, and in great detail in subsequent chapters (methodically examining different categories of evidence in each chapter) James E Snapp Jr. presents a decisive case for retaining Mark 16:9-20 in the Gospel of Mark, and for interpreting it and applying it reasonably to the lives of all believers, as the Christian church has done since the first century of her existence.
And to those who continue to spread false claims after the falseness of their claims has been demonstrated, brother Snapp has one word: REPENT.