super cute! 😊

The faces on both dog characters look 3D at that angle, kinda like they're about to pop out of their pictures and from out of the frames. Neat idea!

One character is favored over the other. Are they brothers or uncles? Are they two sides of the same guy?

Did one of them die within the story?

I guess it's a good thing when your art makes other people think about what could happen, or, what has happened.

It's same character, young and old, for more details we should read the book :)

What's the name of the book?

Don't know, but you can follow them and you will see post with this cover sooner or later
https://www.furaffinity.net/user/kindar

simply wonderful...

V.

Amazingly awesome detail work.
Thank you, Royz.

Ah, just a note, since you say in your descriptions critique/critics are welcome, I think the images here don't quite look like they're printed on flat paper sitting in the frames.
Indicating glass over the pictures if the frames have glass would help (via reflections, smudging from dirty glass, etc.), or in the case of them having no glass you could add some sort of texture to the surface of the paper the photos are printed on, glossy or matt paper, most printed photos have some of of gloss or coating. Because right now they are reading as kind of 3D instead of as photos, especially for the photo on the left given based on your cast shadow direction of the shadow behind that frame, it would be catching a lot of reflective light from the main light source on its surface.

Otherwise, very nice painting, just a minor change or adjustment that I think could improve it a lot. Good work