I wouldn't say there isn't consistency. I would just say that life is more complex and subtle than the Sunday School version of things we were all taught. It's a milk and meat kind of thing.
As I said in another thread, I'm just talking basic, undisputed history and word definitions here.
Are there scriptures that have been lost? Undeniably, you can see them referenced in your very Bible. See the link in my prior comment. As I was reading on this issue today I even ran across a claimed lost
New Testament Gospel that once circulated amoung the Jewish Christians; though I'm not sure how well regarded it was. But don't let that trouble you, the essentials we need were preserved.
Are there differences in the cannon between different Christian faiths? Yes, you can see
a chart here. This is a simple undisputed matter of accounting history. If
you want to start finger pointing about 'changing scripture', we only condemn ourselves as we Protestants were the ones to drop texts.
Even worse,
This may not make much sense to our modern ears, but it is understandable if you were familiar with Luther's context, with the degree to which the RCC had become corrupted and to which the Reformation upturned society. There were many excesses.
Lest we distrust the secular
wikipedia's take, let's take it from the
horses mouth
That last bit is an important note, even the original KJV included many of these books. We don't need to get upset or defensive about it, just take it as an area you can expand your study to become more familiar with the ideas and stories our forebears knew and valued.
Even from the Protestant perspective, these Apocryphal works are still good, being regarded as equal to any other human work. Yet while you will commonly see churches talk about, and hold bible studies around, contemporary books and take them as guides in theology never do you see them do so for these ancient and valued works. Most don't even know they exist. Even I myself haven't read most of them.
I'll stop flogging the dead horse now. Forgive me if this was overwrought, I find history interesting.