As sayings go, “You are what you eat” is accurate. However, I would argue that every book you read also changes you, so that you are what you read. You can’t help but be changed, particularly if you are one of those people who ‘live’ a book (like me).
The relevant equation is: Knowledge = power = energy = matter = mass; a good bookshop is just a genteel Black Hole that knows how to read. – Terry Pratchett
This is an excellent reason for reading, well, just about everything! Don’t read just in your genre. Read textbooks. Read romances. Read newspapers and magazines (even the ones you would never pick up normally). Read Literary award winners. Read graphic novels and most certainly read comics. You will learn so many new things by reading outside your genre, and not just facts. You will see different ways of storytelling and discover new tools for your writer’s toolbox. You will be feeding your muse with plenty of inspiration.
Read inside your genre. Try new authors. Read books that relate to your genre; in my case, anything and everything to do with the Victorian era, and everything to do with science. You will learn how to see the structures and themes that underlie your genre, and how to avoid the clichés and stereotypes of your genres (or you can always turn them on their heads). You will be feeding your muse with plenty of inspiration.
As a writer, feeding your muse is just as important as sitting at your desk and writing. A writer has to be a hungry omnivore of reading matter. And don’t just limit yourself to reading hard copy, as there are plenty of famous short stories and books available for free on the Internet.