For about fifteen years in Philadelphia, Alexander wrote primarily fiction, non-fiction, and translations for adults. Desperate for a job, Alexander worked as a potter's apprentice for his sister. At the end of 1948, Alexander started writing advertising copy and he began to receive more royalties for his translations, leading him to purchase a house for his family in Kellytown. However, he lost his job after three months, requiring his wife to take up employment in a textile mill to make ends meet. Alexander continued to write diligently, though no publishers bought his novels for seven years. One of his short stories, "The Fantastic Symphony" (1949) was published in the "New Directions Annual", a surrealistic piece inspired by Berlioz's notes on the "Symphonie fantastique". Alexander's breakthrough came with his novel "And Let the Credit Go" (1955), his first autobiographical work which he focused on his experience as a bank messenger in his adolescence. He wrote his second novel "My Five Tigers" (1956) about his cats, continuing the trend of writing about subjects familiar to him. He found work as a copyeditor and a cartoonist where he finished his last four adult publications. He wrote two semi-autobiographical novels: "Janine is French" (1959) and "My Love Affair with Music" (1960). Alexander co-authored "Park Avenue Vet" (1960) with Louis Camuti, who specialized in treating cats. The American Society for the Prevention of Cruelty to Animals subsequently commissioned their history, which Alexander wrote as "Fifty Years in the Doghouse" (1964) . During that time he wrote two non-fiction books for children, biographies for August Bondi and Aaron Lopez commissioned by the Jewish Publication Society, the former of which won the National Jewish Book Award in 1959. Alexander's subsequent novel was his first of the fantasy genre: "Time Cat" (1963). He later called it "the most creative and liberating experience of my life". The novel imagines a cat who can visit its other lives in different time periods, which Alexander researched extensively. "Fifty Years in the Doghouse" (1964; reprinted as "Send for Ryan") told stories of how William Michael Ryan saved animals as part of his job as a special agent for the ASPCA.