I recently read the apocrypha books as I also grew up protestant and didn't know about them or read them. I found them to be interesting, but not a big deal, if I can say as much. They seemed to help aid me in understanding the Hebrews a little better, particularly their militancy, such as in the Maccabees. The wisdom books were not as well written or interesting as Proverbs or Ecclesiastes, but they are still pertinent.
As for missing verses, I remember learning about Matthew 17:21 being added, like how GodFatherPartTwo pointed out, there being discrepancies between old and medieval translated books, with the oldest versions of Matthew not containing the part about 'these kind can only come out through prayer and fasting.' I personally find this particular omission fascinating after hearing a discussion that demons could be parasites or inhabit/possess parasites and use them to inflict a person. Makes sense to me and why fasting would be an aspect of the removal of said demons.