Years back, I had to ask a writing friend what she meant when she said my potential mainstream novel lacked depth. I thought I was doing depth because I had several historical romances to my credit already and knew how to bring emotional intensity to the story. But that wasn't it.
She said: "I want more." It took us a while, but in the end I understood that she was talking about detail and imagery. That didn't mean I should plaster the text with lots of irrelevant data. It's the craft of creating a word picture to illustrate what is going on inside your character.
This isn't an easy thing to explain, but I'll try. There was a scene where my heroine returned to the flat she had shared with her dead lover. It wasn't enough to say that she found the emptiness bleak and have her going from room to room. I needed to show the emptiness. Here's an example from the finished book, with the heroine in the kitchen.
"The milk pan on the hob, gathering the scum of days on the surface of the water poured in to keep the burn from sticking; and on the breakfast bar by the window, an open packet of cornflakes, a half-empty bottle of milk, the rest of its contents lumping in decay."
This is the lover's last breakfast, and everything has been left exactly as it was when she heard the news. It's a simple statement of what is there, but it conveys the bleakness of the place and emphasises the loss. There is more of this sort of thing in the bedroom, the lover's study and finally in the living-room, where the heroine at last breaks down.
The trick of this piece of craftsmanship is one of the less obvious ways of showing rather than tellling, but if you can learn to do it, it's extremely effective. Use it when needed, not all the time. Like any other kind of emphasis, it's only effective if it takes us into a different atmosphere from the norm.
What you're doing is using the physical world to take us into the character's interior world. Try it. You may be surprised at the difference it makes to your writing.