I recently got Pure Wool: A Knitter's Guide to Using Single-Breed Yarns.
It's not a massive book - weighing in at 144 pages, it pales in comparison to my Fleece & Fiber Sourcebook, but Pure Wool has a different focus. It doesn't try to be an exhaustive resource for every breed of sheep. Instead, Sue Blacker has chosen 16 breeds found in the British Isles and focuses more closely on their strengths and weaknesses.
The book contains 21 patterns tailored to certain breed-specific yarns. Most of the patterns are quite simple and I didn't find many of them too inspiring - but I didn't buy the book for the patterns. I will say they all look quite knittable and wearable, but many are garments and knit in pieces, so not really up my alley.
I think this is a beautiful sweater, but it's hard to tell
This is a nice sweater knit in Manx Loaghtan yarn... but the pattern isn't included (you can find the Chevron Cardigan pattern by Rita Taylor on Blacker Yarns' website)
My favorite part of the book is the charts in the back - an easy quick reference to the qualities of the wools, substitutions, and the natural colors in which each breed can be found. I'm a sucker for charts and graphs, and these brief charts pack a lot of information into a small space.