Read to Self and Sustained Silent Reading (SSR) are similar in that students are engaged for extended periods of time with books of their own choosing. They typically differ in the teacher's role.
During SSR and DEAR (Drop Everything and Read), teachers often read as well, modeling sustained reading behaviors and the importance of reading self-selected books every day.
During Read to Self, the teacher makes use of the time block to work with small groups or do one-on-one conferring. Because we are unwilling to give up any precious instructional time, we always use the time to meet with students, monitor progress, support their strategy use, and help them think more deeply about the texts with which they are engaged.