Stashbuster Knits: Tips, Tricks and 21 Beautiful Projects for Using Your Favorite Leftover Yarn, by Melissa Leapman, is available in paperback and as an ebook.
That's a good thing, too, because I can see this book being really useful both on your bookshelf and in your knitting bag (and it might fit better on a device in your bag.)
The opening section of the book invites the knitter to consider the yarns in his or her stash, not as just leftovers or guilt-inducing splurges, but as a series of achievements not yet knit.
Leapman lays out a game plan for organizing an unruly stash, complete with a list of different yarn weights and how many strands of thinner yarn can be used together to imitate the look and feel of a heavier yarn.
She then describes a few methods for really getting rid of yarn you won't use, and creating color combinations with the yarns you plan to use. These miniature color wheels, with up to 6 color combinations, are worth the price of admission to a color wimp like me.
When scrap-based projects that work well, they look totally planned. Leapman handles this perfectly. All of the 21 patterns in this book are completely knittable and totally wearable. In other words, they don't look like the knitter was just using up leftover yarn.
Four chapters break up the patterns, by weight of yarn used. I especially like the colorwork and intarsia patterns, where Leapman offers at least two colorways, and sometimes three (often with completely different yarn companies), which is very nice to see.
Overall, a great book for anyone who wonders what to do with those six partial skeins of sock yarn.