Lewis Turco, The Book of Forms: A Handbook of Poetics. University Press of New England. Available.
Mine is I think a second edition: "The New Book of Forms" but there's a third edition out.
Professor Turco has gathered Norse, Welsh, Anglo-Saxon, Japanese, medieval, modern, archaic forms--as many forms as possible--the complaint, the Blues Stanza, the rondeau, free verse, tanka et cetera. The forms don't all rhyme; they don't all count syllables. Since it's a handbook, it doesn't give you subjects or "ways to be inspired" or even pep talks. I sometimes use it to help me pick a form for the poems I write, or help me remember which sonnet is the English and which the Italianate.
I would never sit down and say, "It's time to write a Welsh englyn today!" (except for practice, maybe).
I look through the book, and see if my verse ideas fits a form that might further it. Then I try to give my words that form. If the form makes the soul of the poem disappear, then I don't pursue that form any longer.
Other poets I know don't need this book. They have their method of building worked out, their voice, their way of invoking the soul. And their poems are meaningful and lovely to read or hear.
But I recommend it more than any book for writing poetry I've ever seen. It never tells you what to do; it only tells you what you Can do. It describes where others have been before and found a way to pump up the volume.
----also soliciting other recommendations . . . .