When I first started using Supermemo, it appeared that Incremental Reading was a valuable feature, but I never really used it.
Once I began experimenting with Incremental Reading (Successfully) and adopting the Incremental Reading mindset when I look at learning material, I am now fully convinced of its superiority for nearly all of my intellectual needs. It is light years ahead of its time, and like the core concepts that power Supermemo, eventually it will likely be utilized on almost every level of the educational system (However many years that takes). Until such a time comes, we can rely on the quirky program Supermemo to accomplish this task in a basic way. (I have my own vision of 'the perfect implementation of Superemo,' but I'll save that for some other time)
The only problem is that Incremental Reading in Supermemo works only with a pure electronic text that can be highlighted, copied and pasted. What if you have a pdf file, a physical book, magazine, etc.?
I have recently adopted a crude but (At least for me) workable solution for using the incremental reading mentality to process non-electronic books (Real books), pdfs, magazines, etc.
Simply create a new topic and use it as a bookmark for whatever you are reading.
For example: If I am reading a new Popular Science magazine (That I cannot yet get a digital copy of), I create a new topic within Supermemo and I title it: "Popular Science - April issue". I take the actual magazine and read it until I get bored, have to do something else, etc. If I find an interesting passage, I transcribe the sentence or paragraph into that topic and create an extract of that passage. When I stop reading I make a note of that in the topic; for example, If I stop on page 28 on the third paragraph, I change the topic to say "Popular Science - April issue; Resume on page 28, paragraph 3."
I then place the magazine in a box next to my computer labeled "Incremental Reading." When I see the topic "Popular Science - April issue," I resume reading. Create extracts only of interesting material, read until I stop, change the topic bookmark to reflect my progress, place in Incremental Reading box. Repeat until the magazine has been read.
I realize the proposed solution would not be ideal for all situations, but considering the limitations of the current technology, it will have to do. Also, your reading material (and a highlighter) can travel with you, and you can "save your progress" when you get back to your Supermemo pile.