Sara Zarr shares her (possible) issues in an essay over at Powells.com about the themes that regularly show up in her work. She's not alone, either--many authors revisit the same themes and archetypes over and over again.
Some put it this way: each writer is dealt one hand of cards, and throughout our careers we're playing that one hand in different ways.Of course, writing the same themes over and over again is not the same thing as replicating the same book over and over again. Although that's been done too.
Authors can (and have) taken radical departures from their established norms. For instance, while I knew what Elizabeth Scott's Living Dead Girl was about, I wasn't expecting the experience I got. (Review coming as soon as I can form a coherent thought.) Partly this was because I'd read Bloom and Perfect You and was expecting something closer to that.
But then again, Living Dead Girl did have some very basic similarities to Scott's other work. Not in style, not in subject, but right down in the basic DNA of the story. It was about a girl whose life is a mess and keeps getting messier. Finally, it become so bad she has to decide what the right thing is for herself and for the people that her actions affect.
Overly simplistic? Probably. Maybe boiled down a little too far. But maybe not. There's only so many stories in the world. The details are just around the edges.
Don't be too concerned, Sara. I'd read your sci-fi novel.
Thanks to Bookshelves of Doom for the link.