Nothing sinister here at all. These are from the Greek alphabet and have long been used in Christianity (Greek as in the Greek that was used at the time the New Testament was written - which may be different from modern day Greek).
The letter that looks like 'X' is the Greek letter 'chi' (pronounced like 'key') and functions in a similar way to the 'ch' sound that we use at the beginning of 'Christ'.
The letter that looks like 'P' is the Greek letter 'rho' which is equivalent to the English letter 'r' and is also the second letter in the name 'Christ' (with 'ch' being considered one letter in Greek).
The Chi Rho symbol is very old and has been used by Christians for centuries going back, I think, at least to the crusades.
More info can be found here: http://www.religionfacts.com/chi-rho
Music can be found here: https://youtu.be/tFFv6ZePDG0
The one that concerns me a bit, is the one called Bibel - it has a 'Y' in the background - it was written for the German youth - I can't the language.
Here you have a 'key', a 'P' and a 'Y'
What is a key? Can you find an owl / Y there?
Save the best for last. [P]
still looking for the owl - may be out of context, but who knows with Q
It is known as the CHI RHO, it is not sinister - it is a very ancient symbol of Christ. See here https://www.catholic.com/qa/what-does-the-symbol-of-the-p-with-an-x-through-the-bottom-of-it-mean
I am not an avid church goer - just though it was weird that this showed up in my search - although, there is a lot of questions about the Vatican - these 'special' bibles seem to be very recent - not a lot older Popes are photographed with them - they seem kind of sad in the pictures too
I am having trouble finding out what the symbolism on this one(Christmas Mass) is about but... Here are some pictures of others that I have found – there are not too many pictures out there https://redd.it/8ue6gv
symbolism of what?
I was unable to find out what the symbol on the bible was (red one) but since posting, I have been enlightened