iStudiez Pro is a very flexible app that can be accommodated to many users' requirements.
For example, "class" in the app is a planned event, that happens on a certain date/time. It can be either your study classes or any other activities, like personal appointments, gym visits, etc.
This way "assignment" is also not just a study assignment/homework, but the task you have to do, that can be marked as completed once done.
Basically, using standard features and option of iStudiez Pro you may use the app for various purposes.
If you need to have a separate To-Do List, or Reading List, add a new course > name it, like "To-Do List", "Readings", etc. and using the Assignments feature add the list of things you have to do, or the list of books you have to read.
Once done - mark assignment as complete.
Disable the Grade option for this course (Planner > Schedule > Semester > Course > Grades > uncheck the "Grades" option) in order not to be prompted to enter the grade once you mark "assignment" as done ("completed").