This is the second book of the Mishneh Torah of the Rambam, Rabbi Moshe ben Maimon. Laws of Reading the Shema.
This chapter explains the law regarding how far one should concentrate on reading the Shema, whether the reader should be walking or face the ground, whether the worker should stop their work to read, whether the Torah student or congregator should interrupt, whether the one who went down to immerse should read in their place, whether they can read naked, whether they should listen to the reading, whether they can read in any language, whether one should be precise with the letters and how to be precise, whether one reads backwards or reads the sections in a different order, whether one read intermittently or asleep, whether one doubts whether they read or not, whether one read and made a mistake should return, whom one can greet between the sections and what the sections are.