This is a tough one, I thought about it most of the day and while I have favorite authors such as Marian Keyes, George R.R. Martin, Charlaine Harris, Neil Gaiman and several Indie authors the writer I admire the most is Maeve Binchy.
Maeve Binchy is an Irish novelist with 15 novels and many short stories to her credit. The first novel I read from her was "Evening Class", when I checked out the book the librarian made a comment about how great a storyteller she is and the librarian was so right!
My admiration for Binchy's style lies in her ability to transport the reader into a peaceful state of mind in which we can forget the world surrounding us and dive into her characters' world. Most of her characters are interconnected through out her novels, so when you read "Minding Frankie" (released 2010) you get to see what's going on with Ania whom you met in "Heart and Soul" (released 2008), the cute Fiona from "Nights of Rain and Stars" (released 2004) and even Nora and Aidan, the adorable couple you fell in love with in "Evening Class" (released 1996). It's like visiting old friends, it's really lovely!
As for mentors, I mainly have cheerleaders, other writers whom I've met at the coffee shop or online. I haven't joined writing groups because writers tend to think too much of themselves and want to talk only about their work. Of course, this rubs me the wrong way since I only want to talk about MY work and they should be fascinated by me, right?