Consider adding LED strips to the bookcases to brighten up the shelves

Use keep it light. The grey.

I would keep your hallway as light coloured as possible, if traffic is not too bad, read lots of kids and pets. There are warm whites that will coordinate with your beautiful bookshelf colour.
I would paint everything the same colour. Ceiling, walls, trim.
It will look fresh and crisp. Add a beautiful, colourful runner down the narrow hallway, or if you want something customized for your entry area you could use "Flor" carpet tiles that form a rug and can then be cut to size.
I would add beautiful ceiling lights as well if budget allows...

What about something deep and dramatic? I scribbled some teal on your hall wall just for fun. Not suggesting teal but wanted to try something rich. I think it adds some fun drama to your little space. Sorry it's so rough looking.

A couple of art pieces and a gorgeous runner would really set it off as well!

That's a really interesting idea. I hadn't even considered painting the back of the bookshelves a different color. Thank you.

Here is a better looking example of what I had in mind:

Beautiful. Thank you.