THE LODGER By Louisa Treger Thomas Dunne/St. Martin’s. 262 pp. $24.99 Louisa Treger’s earnest, carefully researched first novel spotlights a neglected pioneer of 20th-century literature: Dorothy Richardson, who published one of the earliest examples of stream-of-consciousness fiction, “Pointed Roofs,” in 1915. Fellow modernist Virginia Woolf praised her for inventing “the psychological sentence of the feminine gender,” and the best passages in “The Lodger” show Richardson developing a distinctive prose style to mirror “the mind of a woman,” which is “deeper, more instinctive . . .