That may depend on the quality of your reading. I'm not just saying that if you read a badly written book, it can be harmful for your own prose. That's obvious. Sometimes the harm can be done also by a very well written book, which has nothing to do with your own writing. There's a slight risk that it can be somehow contaminated.
It's a fact that the more you read a certain author, the more you tend to write like them. This can be a problem for writers who haven't got yet a strong voice or are still unsure about it.
It can happen that various novels of an author sound different, because of the different kind of reading they do during their writing periods. This is not a completely bad thing, as it's a way to explore your skills and actually find your voice, but sometimes it can make you feel quite weird.
It is, instead, a serious problem when you are writing a series and want your style to be as much consistent as possible along all books.
How to manage this situation?
My suggestion would be to be very various in choosing your readings. Change often author and genre. Read a lot during the period in which you are not writing and slow down a bit while you are writing (this is also natural, as you are supposed to have less time). While you are writing, choose books which are more consistent in style to your prose, even if from a different genre, or vice versa, i.e. very different style but same genre. This way your mind process this new input separately from your output.
But there's also another way to avoid bad influences, which is feasible if you speak at least one foreign language: read books in that language, possibly in the same genre.
This way you risk less to have your style contaminated, though at the same time you are assimilating narrative techniques, structures, rhythm, new ideas, all of them can be then reprocessed through your own voice into something really original.
That's what I'm doing lately. As you know, I write in Italian (my mother tongue) and I'm writing a series of four books ("Deserto rosso"). I'm almost half way with the third one now. It was quite difficult to me to start writing this one, as months passed after the first draft of the second book, I had written another novel in the meantime (experimenting a new genre) and I’m reading a bunch of different books, which I’m mostly loving but have nothing to do with my still fragile writing voice. Then I decided to concentrate most of my reading on English books of the same genre of my series (sci-fi), which boosted my fantasy and my creativity, and my feelings about my story, without strictly influencing the kind of words I prefer to use or the way I like to use them.
It's also true that, as an author, I must continue improve my vocabulary and let grow my style, otherwise all my future books could become a bit repetitive, but this is a much slower process which doesn't happen overnight.
much helps you increase it, but not all readings are the same and not
all of them might be suitable for you. Reading
What about you? Do you read books in foreign languages? How the books you read while writing influence your own style? How do you choose them?