Bird By Bird by Anne Lamott
On Writing by Stephen King
Aspects of the Novel by E.M. Forster
Close cousins to these - also enjoyable in the writerly mood - are:
Letters to Alice on First Reading Jane Austen by Fay Weldon (for her riff on writer-built The City of Invention) and
A Room of One's Own by Virginia Woolf
Follow with the funny just-finished-writing-the-novel book:
The Unstrung Harp by Edward Gorey.