Richard Booth, who collected a million titles to transform a fading 12th-century Welsh market town into a mecca for secondhand book fanciers, and who celebrated his improbable success one April Fools’ Day by crowning himself with a title he concocted — “King Richard Coeur de Livre” — died on Aug. 20 in Cusop, Wales. He was 80 .

An obituary placed by his family in The Hereford Times said that Mr. Booth “died peacefully at home” in Cusop, which straddles the eastern border between England and Wales and adjoins his so-called kingdom of Hay-on-Wye, where he had made a career of playfully, and often constructively, disturbing the peace.

“Booth is, with justification,” Jane Frank of Griffith University in Australia wrote in a 2018 study of regional economic development, “regarded as the person single-handedly responsible for reviving, with immense charm, this dying Welsh country town and leading the international Book Town Movement with enormous dedication .”

His face framed by mussed black hair and black-rimmed glasses, Mr. Booth was what The Guardian called “a British eccentric of the best kind”: an Oxford-educated Barnum of books who, the newspaper wrote, “never reined in his passion for the eye-catching and entertaining, the wacky and the wonderful.”