My favorite book of all, oddly enough, is just a visual reference from Winsor & Newton about mixing watercolor. I frequently use it for digital paintings as well when I need to make a palette for a new painting or one I'm stuck on. I bought my copy from DickBlick.com some years ago for several dollars, but it is available on Amazon.com for what seems a very expensive $16. It's really not a large book so I would buy it used or with a coupon, it's definitely not worth $16 even if it is handy. It is $1 cheaper at DickBlick.com.
My next favorite is Stephanie Pui-Mun Law's Dreamscapes. I linked to the Kindle Edition because it was the first to come up, but I recommend the paper version. I hate e-books though, so take that with a grain of salt. Even if you don't learn anything from this book you can't help but be inspired by it.
I also love Linda Ravenscroft's books, particularly this one. I've had it for ages but I always go back to it for whimsical inspiration.
My favorite non-instructional and purely inspirational watercolor books are Amy Brown's books and Brian Froud's Pressed Faeries. The Pressed Faerie books were hard to find for a while (about 10 years ago) and I spent several weeks tracking them down and ordering used copies, but I have a few of them now and they are worth the work. The hardcover is the best.
When it comes to watercolor itself my favorite paints are Holbein (tube), Winsor & Newton (tube), and Yarka pan/cake paints.
A note about sprinkling salt, rubbing alcohol and so forth on your watercolors to achieve different effects: These methods change the ph of the paper and ruin any archival quality they might have, so keep that in mind before you do it!