Now that I see your space, it is a dilemma, I suggest true bookcase speakers (not small monitors called bookcase these days) horizontal on those shelves, keeping all drivers at same height, as low as can be achieved.
How DEEP are those shelves ____?
My office speakers, 3 way, 10" woofers (a lot more bass than typical small speakers with 6-1/2 inch woofers.

Ideally located at seated ear height like mine, but you have higher shelves. Depth needs to fit a shelf, height not too high for a shelf space (you have no height restrictions), and you do not want ports, if so front only
Mine are vintage AR-2ax’s restored quite easily, or buy some already restored by someone else. Everything needed is readily available.
Local Pickup Only, you could use UPS Pack and Ship, seller simply drops them off, unpackaged, UPS packs and ships, they responsibile for any damage. I have used UPS successfully a few times.
They have level controls for tweeter and mid volume control relative to each other and the woofer, which will be an asset in your use.
You can put a small block under the rear edge, angling them down a bit, for better sound ’down there’ and alter the reflection off the ceiling, avoiding strong secondary waves and eventual rear wall waves.
Of course, any new speaker that can be used horizontally can be likewise used, but most do NOT have level controls, a true asset of the AR-2ax’s and likely a benefit in your space/high location.