I had heard this advice from a number of writers but was not completely convinced as to why a writer should read a lot in her genre. My hesitation was coming from the thought that if I read a lot in my genre, it might influence my writing and take away the originality from it.
Recently I came across some books in my genre which were written in a non-traditional style (that I seem to prefer) and I read them as well as enjoyed them. Contrary to what I believed earlier, reading these books doesn’t necessarily take away originality in my writing because I have my unique voice and I would continue to write in that voice of mine. However, reading books in the same genre or watching movies in that genre is stimulating for a writer. It creates the right stimulus for the creative juices to flow.
Reading books in your genre can also be looked upon as practical learning where you are looking at different styles of writing. For example, I came across a book where a short scene was very powerfully written. In addition to theoretical learning of the craft by attending workshops, practical learning by reading books in your genre is a way to grow for a writer.