Outlining and mapping tools can help you organize main ideas and details to improve your comprehension.
Outlining tools
MS Word and Google Docs have outlining features built-in
Workflowy (free or paid) is a web-based outlining tool with features that enhance focus (expand or collapse) and act as a task-manager (hide completed bullets)
Visual mapping tools
Mindomo is web-based (3 maps free, then paid subscription)
Mindmeister is web-based (3 maps free, then paid subscription)
Inspiration is installed software or web-based (paid download or subscription)