Why is it important for a writer to read? There are several reasons.
One, there is nothing new under the sun. Stephen King’s novels and short stories borrow elements from other writers; Shakespeare’s plays took plots and characters from the Greeks and from fellow playwrights. Whether you are writing a novel, a letter, a resume, a research paper — reading others’ works will give you material and insight.
Two, reading others’ works teaches you a lot about structure. Want to find out how to write a good fantasy novel? Read some Robert Jordan, and some Tolkien, and some G. R. R. Martin. Look at what they each do to build suspense, to develop character, to move from one part of the story to another. Writing a cover letter? Find some examples. You want to look at the **structure** and not just copy what you’re seeing (that’s plagiarism!).
Three, language is always changing and growing. Reading others’ works keeps you informed of what (grammatical) rules are being followed, and which ones people are experimenting with. Keeping up an active reading habit will let you catch misspellings and awkward phrases without having to dig out a dictionary.
The most important part, though, is to be intentional and self-aware about what you’re learning from other writers. Be sure to add your own spin to what you’ve learned. After all, Shakespeare is Shakespeare because he took his sources and added his own insights, voice, complications to them!