A software-assisted method for learning and retaining information from reading, which involves the creation of flashcards out of electronic articles. Wikipedia 
Reading falls into a bucket called "Passive Learning", but it's how you deepen your understanding. The problem with most reading is that it's hard to convert readings to notes. It's even harder to then convert those to effective flash cards for "Active Recall". Without spending this effort, the knowledge you gained fades.
Incremental Reading tools encourage you to read incrementally. You read a few paragraphs and that might be enough for now. You reword the work to make it clearer in your mind. When you've read it enough you may choose to make flash cards to get that knowledge memorised.
I get a feeling that this is what Michael Neilsen was doing when he described "Deep Ankification" in his article "Using spaced repetition systems to see through a piece of mathematics". Article
There's a huge book-like manual on incremental reading that's been published on Supermemo. Manual Archive
See also Incremental Learning.
Tools
Supermemo , Windows only.
Dendro , Italian cloud hosted tool.
Polar Bookshelf , used to be GPL. Project Fork
There's a plugin for Anki that's really badly built. There's also a discussion about implementing this in Anki directly. Thread