Today it's authors.
I was thinking about the books that have influenced me over the years and it dawned that it wasn't so much the books as the authors, hence this list.
1. Stephen King
This man is at the top of the list for one book: 'On Writing'. It is by far the best book ever written on how to write and is also partly a biography. His no-nonsense style tells you in simple terms that you already have the vocabulary you need, and the talent, that you need to learn as go along and keep at it. There's a bit more to it, but that is my summary.
You won't find anything about a 7 point plot plan or 20 master plots and their derivitives, just plain, simple advice on how to write well. This is backed up in the second book of his that I've read, Insomnia. It moves along at a cracking pace, yet is still 600 pages long. Simple words used very well to tell a harrowing tale of death and paranormal destruction.
2. Tom Holt
A British Fantasy Comedy writer whose style is similar to that of a stand up comedian: drag the moment out and hit the audience with the punchline. As a result his humour doesn't always work and in his earlier books the endings can be a little lame. Despite that, he has over 20 books in print all of which have taught me the value of comedic description and given me some insight into improving my own writing in this area.
His latest book, Blonde Bombshell, is a peach of a tale and if you want to find out what happens when someone confuses a lightsaber with a torch, this will entertain you till the last page.
3. Robert Harris
I came across his first book, Fatherland, years ago when it first came out. His pacing was superb, his characters believable and the storytelling sublime. There are no wasted phrases or over-colourful desriptions here, just good story telling. In many ways he is similar to Stephen King in his talent and style, but he writes political thrillers.
His last book, The Ghost, is a superb example of his story-telling ability, concerning a writer brought in to finish the biography of a former British Prime-Minister who bears a remarkable similarity to Tony Blair. The author himself said in a radio interview the similarity is deliberate.
Other influential authors include Terry Pratchett, Douglas Adams, Craig Thomas, Alastair Reynolds, Isaac Asimov, Aldous Huxley, George Orwell and Arthur Conan-Doyle.