There was a lovely piece by Michael Erard in the New York Times a couple of weeks ago about how we tend to echo the styles of the things we read most often. It's called "structural priming" or "syntactic persistence" (I love both these terms), and it's almost like muscle memory, how our brains form habits in relating words to each other in predictable patterns.
The author's point is that we need to cross-train, as it were, to experiment with different genres and voices so that we don't become too stuck in our own. I thought it might be useful to think of this the other way round, though. If I'm struggling (as I am) to craft a book manuscript, and I wonder occasionally if my writing isn't getting a little too lumpy and stiff, wouldn't it help to treat myself to regular exercises of reading the writers I most want to sound like? The first two that come to mind are Tim Egan and Garrett Mattingly, both of whom are masters of compelling and lively nonfiction. Who would you read to teach your brain some new tricks?