I think the best simplest solution to this problem is something you will of heard before but this simple method can improve your comprehension of what you've read by up to 70%.

You simply grab a pen & paper and take notes as you read a chapter. The sheer act of writing takes you from passive to active and triggers your brain to focus and think what your writing.

So you buy a note pad and every book you read you write notes doesn't have to be extensive just write the key points out.

This will greatly improve your ability to remember a subject. Passive reading is rubbish for trying to remember a subject especially if the topics a bit dry.

Another quick way of remembering is to take notes using Mind Map. It works for me. One such tool is freemind and another commercial tool is Think Buzan's iMindMap (You can get a non commercial version with some limitations) for your personal use.

Hope it helps.