Pollyanna by Eleanor H. Porter (1913). The novel that put Littleton on the literary map, written by a woman who grew up here. Pollyanna is an eleven-year-old orphan sent to live with a cold aunt in a thinly disguised New England town — optimism as a survival strategy, not a personality flaw. Reading it before or after walking past Porter's birthplace on Main Street sharpens both experiences. The follow-up, Pollyanna Grows Up (1915), is worth reading too.
A Walk in the Woods by Bill Bryson (1998). Bryson's account of hiking the Appalachian Trail passes through New Hampshire's White Mountains — the stretch that frames Littleton's backyard. Funny, digressive, and genuinely informative about the trail and the culture around it. The section on the White Mountains captures the particular exhausting beauty of the landscape that surrounds the town.
North Country: A Personal Journey Through the Boreal Forest by Scott Weidensaul (1996). An ecologist's close reading of the vast northern forest that Littleton sits at the southern edge of. Weidensaul follows the seasons through the boreal zone, writing about birds, moose, rivers, and the people who live in and around this landscape. It gives the region around Littleton ecological depth that most travel accounts miss.