Active reading. First scan TOC and headlines. Then read superficially. Grasp the author’s leading propositions by dealing with his most important sentences. Ask questions while reading.

After reading a certain amount of text, close the book and summarize in your own words what you have read. Again ask questions how the key ideas relate to what you already know.

The ultimate exercise is syntopical reading where you compare several books on the same subject with each other.

Best intro: "How to read a book" by Adler.

P.S: I'm very interested in this subject, I'm trying to build an app to support active reading.

Edit: re-reading your question, you seem to want to read faster and consume as many books as possible. As you can guess, my advice is the opposite. Read slow but deep and fewer books (just pick the best out there)