Suggestion for rear speaker placement

I am currently designing my very first HT. The room is not HT dedicated. It is a library. Room size: 19'L x 11'2"W x 8'H. Initially, I plan on 5.1 speakers.
I will be forced to place the 2 rears on shelves 5 feet high from the floor behind the listening position on either side of the doorway (French pocket doors).
1) Is this placement a good idea, as oppose to in/on ceiling?
2) If I do place it on the shelves, should I angle it towards the listening position? How do I angle it? Piece of wood? Are there special mini stands that angle it?
3) What would be good speakers to do this? What brand and model would be good for such placements? Are there speakers optimized for this kind of placement? I cannot be the only one with this issue.

I have not auditioned that many speakers; so far, I like the Reval M20 for FR and FL and the C30 for center and the B15 Subwoofer.

I plan on building in July, so any help would be greatly appreciated.