I fell in love with the sweater on the front page of Color Style. So I decided to buy the book. Amazon told me it wouldn't arrive till end of May, but here it is, full of nice, colourful patterns. But the front page sweater is still my favourite.
The other book, The Essential Guide to Color Knitting Techniques
by Margaret Radcliffe was recommended to me on Ravelry by fibercrone (ravelink). I've loved colour knitting for many years, and when it comes to stranded colourwork I consider myself quite experienced. But there are so many other techniques... I really recommend the book!
And on top of that, I found a book that had been missing for a long time, Maskeball. That's another favourite!