In a project about the grammatical development of adult second language learners of Swedish, I examine textbooks used in Swedish for immigrants, from the perspectives of processability theory and different measures of complexity, such as subordination and noun phrases. Several language acquisition theories point out the importance of input one step ahead of the learner's current proficiency level in order for development to take place. It is therefore relevant to investigate if the input, in this case the textbooks, that the adult learners are exposed to, follows the developmental stages defined by processability theory and increases in complexity.