Knitting Without Tears - Elizabeth Zimmermann
(What can I say? This book changed my life. I'd been knitting for years before I saw it,
but this book gave me the courage to design my own sweaters, rather than just alter
others' patterns. I almost put this onto the general knitting list, but I think it really
belongs in the design guide category.)
Designing Knitwear - Deborah Newton
(A revelation and an inspiration.)
Knitted Embellishment - Nicky Epstein
(Also look at all her other books - I'm putting this in the design category because by
using her imaginative ideas as an inspiration, you will be designing your own knitwear)
The Mary Thomas and Ida Riley Duncan books also belong here because they give
you much more than just patterns. They teach you to design your own.