Reading in 3s is a way to structure reading a text so that you cover it 3 times over, sequentially. This is easiest explained by a 3-page model: you read 3 pages, but you only move your bookmark forward one page each session. Thus, you’re always reading one page ‘fresh’, one page ‘revision’, and one page ‘I totally get this now’.
But what I’ve found personally is that this has drawbacks – you must read the same amount of text each session, otherwise it gets messed up, and you need to work with a portion of text that’s relatively divisible into 3. So if you want to go up from 3 pages, 6 pages is your next best bet, but that’s double the amount.
Lately I’ve been working with a more flexible approach – I just use three bookmarks. The first bookmark means “everything prior to this you’ve already read 3 times”, the second “everything prior to this you’ve read twice”, and the third, “everything prior to this you’ve read once.” So for any given reading session, I open up at bookmark no. 1 and read from there. If I pass bookmark two, it doesn’t matter, wherever I stop I just place the bookmark (i.e. you don’t need to label your bookmarks 1, 2, 3, but if you did you’d need to move them sequentially). And I always know that those bookmarks mean the same thing. If, perchance, a day’s reading doesn’t get past bookmark 2 or 3, this doesn’t matter so much. And, if I’m feeling adventurous, I might leave bookmark 1 in place, and start with bookmark 2. Et cetera.
You do need to be a bit more intentional – you still want to balance the general proportions of new/revise/revise, but it gives you more flexibility for reading more or less on different days.
It also opens up the possibility of ‘reading in 4s, 5s, 6s’. I.e., you can just add more bookmarks. You might, for example, decide that a particular text is worth more revisions, and so your main 3 bookmarks are around chapters 13, 14, 15, but you start another two markers at chapter 1. Then on any particular day, you can treat these two groups separately, advancing the bookmarks in relation to each other. And if bookmarks 1 and 2 ever catch up to the other 3, you’ll know that you’ve now read that whole first portion 5 times over.
Great for building a lot of comprehensible input, especially with a well-graded text (I mainly use this with Italian Athenaze and Roma Aeterna at present, and it’s been serving me quite well.