Jenny Uglow's new biography Nature's Engraver: A Life of Thomas Bewick (Farrar, Straus and Giroux) is one of the best examples of the genre I've read this year. Uglow has captured the spirit and nature of Bewick remarkably well, and the text is nicely complemented by the many delightful examples of Bewick's woodcuts scattered throughout.
Beyond the straight retelling of Bewick's life and business (interesting though that is), Uglow provides a well-researched look at the history of book illustration in England and the gradual development of the various engraving processes which Bewick largely scorned in favor of the more traditional woodcut (a form of which he must be counted one of the great masters). The book charts his rise from "wild child" of the English north to acclaimed illustrator, in high demand by the top publishers and authors of England.
A short section in which Uglow discusses Bewick's impact on some other British literary figures (Wordsworth, the Brontës, &c.) was particularly fascinating, as was her recounting of a meeting between Bewick and John James Audubon (two great artists whose styles were infintely different, but each marvelous in its own way).
Importantly, Uglow also takes us beyond Bewick as artist and naturalist, giving her reader a view of the man which most of his contemporaries might not have had: an unorthodox deist in religion, Bewick was also fairly radical in his politics, joining many of his Newcastle neighbors in actively supporting pacificist principles and political candidates during the American Revolution and the Napoleonic Wars. For people like Bewick, best known for a single occupation, I think it's easy (at least it is for me) to see them in a sort of vacuum, just doing their thing; Uglow's book does a good job of adding those additional dimensions that often go unconsidered.
I'll add my obligatory comment about the unsatisfactory citation style (references go unnoted in the text), but that's the only minor fault with this excellent biography.