A writer needs to be a reader
If you're struggling to find the time to write, you may think it's not worth finding the time to read, but reading widely is vitally important for any writer.
In his book 'On Writing,' Stephen King outlines his writing process - he writes in the morning, and spends the afternoon reading. As one of the most successful writers of all time, he knows what he's doing.
1) Market research
Knowing what is out there, what publishers like, and seeing what sells helps identify the market for your own work. In some instances, it shows what to aspire for, and sometimes, you know you can do better. When you pitch a novel, many publishers like you to explain how it fits with their already published works.
2) Identify & emulate writing styles
Each author has their own distinctive style. By reading widely, you begin to see those styles, discover which ones you like. Then as you read, you can deconstruct their style and discover what works well. A fast paced action novel will use plenty of verbs, and spend less time on description. James Patterson uses short chapters, and hooks at the end of each to lead you to the next. Look at the choice of words; the length of sentences. What can you learn about how the writer uses language that you can take into your own writing?
3) Understand genres
If you plan on writing in a particular genre: Romance; Sci-Fi, Fantasy, Thriller, etc, you need an understanding of the tenets of each - how do they work? Fantasy readers will expect new worlds or magic, or mystery of some description. How does the satirical comedy of Wodehouse and Sharpe work?
While originality is essential for your writing, it still needs to be firmly grounded in its genre. Read the classics from each genre, work out what makes them fit in.
4) Learning what you like
Reading widely helps you identify what type of writing you like. it is most likely that you'll write something of a similar ilk. If you hate reading bibliographies, it's unlikely that you'll enjoy writing them. Your favourite type of writing is most likely to be the type that you'll enjoy writing. I never thought I could write fantasy, until I read Trudi Canavan, an Aussie writer with a fabulous style who writes very different fantasy. Her Black Magician Trilogy inspired me to start writing my own Fantasy / Sci-Fi novel (currently in editing phase)
5) Creating characters
Which characters did you like? Which did you hate? Which stayed with you? Liesbeth Salandar in the 'Girl Who played with fire' is a psychopath, but the reader sympathises with her, and accepts her actions as justifiable - that's not a combination which is achieved easily, and it's worth looking at how Larsson accomplishes this. Look at how the characters develop through a series. The reader builds a relationship with a series, and will wait eagerly for the next instalment, either in a trilogy (Trudi Canavan) or mult-part story such as Game of Thrones. GRR Martin is not afraid to kill popular characters! Terry Pratchett created a whole world, and populated it with characters who reoccur. I never thought I'd love Death so much! Then there are characters who appear in multiple books, such as Janet Evanovich's Stephanie Plum, or Kay Scarpetta in Patricia Cornwell's novels. These are substantial, enduring and completely different characters. Stephanie is accident prone and torn between two hunks. Scarpetta is the ultimate professional. Reading authors who create compelling characters will help you create your own.
6) How an audience shapes writing
If you're writing for publication, then you're writing for a specific audience. Children's books use simple language, and lots of repetition. The word counts and vocabulary are both very limited - up to 500 words for picture books; 30 000 for young children; young adult around 60 000. A Mills and Boon is around 55 000 words, and Fantasy tends to start at around 80 000. Are you writing for men or for women, or both? Which characters will appeal to your audience? What are the interests of your audience? What type of language do they use? If you're writing for young adults, do you have a grasp of their language: whether cool is hot or hot is cool? Reading books for different audiences will help you understand how to write for that audience.
7) What doesn't work
We've all read novels which we hated. Why didn't they work or catch your attention? '50 Shades of Grey' was a publishing sensation, but is highly improbable, poorly written, but sold millions. Of course, now you can't give them away! You can learn a great deal even from the novels you don't like.
8) Read Prize winning authors
The calibre of their writing has been validated by their peers, the publishers and the public. Sometimes they push the boundaries. Sometimes you'll hate them. Sometimes they'll stir your emotions. Read to see how they did it. What made the book so successful?
There are also the exceptions to every rule, those books that defy convention, and are enormously successful. To find them, and write them, a writer needs to be a reader. Read to learn, hone and refine your craft.