"Dua Libro de l' Lingvo Internacia" by L. L. Zamenhof is a language textbook published in 1888. It is the second book about the constructed language Esperanto and the first written entirely in the language itself. The work provides translations and reading material for early learners while solidifying Esperanto's final grammatical form. It includes texts, model sentences, fairy tales, sayings, and poems to demonstrate the new international language in practice.