The most important book/audio that I have read/heard is 'Awareness' by Anthony De Mello. Tony, as he was known, was a Jesuit priest. But 'Awareness' is not a Roman Catholic text/talk. Nor is it Zen or Taoist or any label beyond 'spiritual.'
There is a book but the book is actually an edited transcript of a retreat that Tony held and that was recorded. The audio works best. It's long, nearly 9 hours, but I highly recommend that you listen to it. For me (and for many others) it has been life changing.
The best place to start is with the Tao Te Ching, of course. I was introduced to it by a friend, Angela Joiner-Handy, who was working with me in the late 1990's. She saw that the preface of her copy mentioned aikido and, since she knew I was doing aikido, thought I might be interested. What a gift she gave me.
The version she introduced to me was a translation by Stephen Mitchell. I don't know that it is the 'best' translation but it is an easily accessible one. You can buy a copy of his translation or there is an apparently legitimate, non copyright-infringing online version.
If you want to see how different the translations can be then this website has an extensive list of English translations. This is another good website with a list of Taoist resources.
If you want to read a version written in clear, modern, no-nonsense English then take at look at Ron Hogan's free online version.
If you want to learn a bit more about the origin of the Tao then the great Alan Watts does a thorough introduction in this audio only YouTube video.
Finally, a fabulous exploration of Tao in an easily accessible way is 'The Tao of Pooh,' by Benjamin Hoff. I love this book because it combines two of my most favourite things - Winnie the Pooh and Tao.
My friend, Kensho Furuya, recommended that I read this book and so I pass his recommendation on to you: 'From the Zen Kitchen to Enlightenment.' This book was written by Kosho Uchiyama who was the abbot of Antaiji Zen monastery on the outskirts of Kyoto. You can see the monastery in action in the video below:
Below are a few more talks by Alan Watts on Zen. He has a brilliant way of explaining the complex and confusing in a simple way. He has also written books on Zen that, though I've not read them, I am sure are excellent.
This is an old video from the BBC: