I finally found a copy of the definitive one-volume H. P. Lovecraft biography I could afford.
(Lovecraft, H.P.) Joshi, S. T. H. P. Lovecraft: A Life. Necronomicon Press, 1996. First edition, one of only 250 signed hardbacks (the only hardback edition), a Fine copy in a Fine- dust jacket with a very tiny wrinkle at head. Widely considered to be the definitive Lovecraft biography until Joshi’s two volume expansion I Am Providence (which I also have) came out in 2010. The hardback of H. P. Lovecraft: A Life peaked around $500, but has since drifted down a bit. I bought this one from the publisher off eBay for $160.