A native of northeastern Mississippi, Hamblin first read Faulkner's works in T. D. Young's Southern Literature class at Delta State University in 1959. Later he earned his master's and doctorate's degrees at the University of Mississippi in Oxford, Faulkner's hometown, completing both his thesis and dissertation on Faulkner topics under the direction of John Pilkington, author of The Heart of Yoknapatawpha, an influential study of Faulkner's major novels.
In 1978 Hamblin met Louis Daniel Brodsky, a noted Faulkner collector who lives in St. Louis, and since that time the two men have worked together to produce Faulkner: A Comprehensive Guide to the Brodsky Collection (5 vols., UP Mississippi, 1982–88) and other books, articles, exhibits and public lectures based on the materials in the Brodsky Collection. In 1988 Southeast Missouri State University acquired the Brodsky Collection and established its Center for Faulkner Studies to oversee the use of the materials. Hamblin has served as the director of the center since its creation.
Hamblin has directed Faulkner seminars for both the National Endowment for the Humanities and the Missouri Humanities Council. He is one of the originators of the "Teaching Faulkner" sessions at the annual Faulkner and Yoknapatawpha Conference and edits Teaching Faulkner, a newsletter devoted to the teaching of Faulkner works in university, college and high school classes. He has co-edited, with Charles A. Peek, A William Faulkner Encyclopedia and A Companion to Faulkner Studies; with Stephen Hahn, Teaching Faulkner: Approaches and Methods; and, with Ann J. Abadie, Faulkner in the Twenty-First Century. In 1997 he delivered the keynote address at the Faulkner Centennial Celebration in New Albany, Mississippi, Faulkner's birthplace.
In addition to his Faulkner work, Hamblin has published two volumes of poems, From the Ground Up: Poems of One Southerner's Passage to Adulthood (www.timebeing.com) and Mind the Gap: Poems by an American in London (www6.semo.edu/universitypress); a sports biography, Win or Win: A Season with Ron Shumate; and critical essays on Robert Penn Warren, Willie Morris, Pat Conroy, and W. P. Kinsella. He serves as poetry editor of Aethlon: The Journal of Sport Literature and as associate editor of The Cape Rock, a little magazine of poetry.
Hamblin is a past recipient of the Southeast Missouri State University Alumni Association's Faculty Merit Award and a Governor's Award for Excellence in Teaching. In 1998 he received the Missouri Library Association's Literary Award, and in 1992 he received the Halsell Prize from the Mississippi Historical Association for the best article of the year published in the Journal of Mississippi History. He has been awarded research grants from the American Council of Learned Societies, the National Endowment for the Humanities, and the Southeast Missouri State University Grants and Research Funding Committee. He has taught as a visiting professor in London and Maastricht, the Netherlands.