Aimed towards advanced students and researchers in language acquisition and teaching, Language Intake: Understanding and Improving Language Learning and Teaching considers the long-debated definition of language intake and its determining factors, and in doing so presents a unique argument for language input and intake, with a particular focus on how 'input', 'interaction', 'identity', and 'investment' contribute to intake through complex intercommunication.

The book defines each of the contributing factors of intake in turn and demonstrates the principles of language intake through interviews with successful language learners, in order to encourage teachers to take into consideration these factors so as to maximise intake that allows for comprehension of the target language, along with its rules of use, and integration into a learner's internal grammar.

Griffiths proposes that all these multiple factors contribute to what might be called the "Intake Hypothesis", which can be outlined as a practicable framework to support teachers in providing rich, interesting, and extensive input, affording opportunities for interaction, respecting learner identity, and offering a motivating environment to encourage and sustain investment of time and effort, thereby contributing to intake.