(Note, I tried to make the subject line read, "Books>Kindle>Audiobooks", but for some reason, Slashdot removed the ">"s.)
I absorb least of all from audiobooks, only partly because I usually fall asleep in the first five minutes.
Ever since the Kindle app got rid of the little graphical representation of where you are in the book (like a timeline, at the bottom, where you saw whether you were 1/4 of the way through, halfway or close to the end), I've been a little uncomfortable with my ebooks.
Say what you will about those old paper-and-board book things, at least you knew exactly where you were, and could get some mental image of the progression of the narrative arc. So when you'd only got maybe 1/10th of the book read (based upon the fact that only a little bit of the book was on the left hand side) and you were reading a mystery, you could pretty much rest assured that there were some pretty big plot twists to come. Maybe that has something to do with any less absorption from ebooks (if there really is less, which I doubt this study proves).
Even so, I read mostly everything on a tablet, except sheet music. And when a really good sheet music e-book reader (and editor) comes out at less than $2000, I'm going to grab one. Musical manuscripts are just too small, even on a 10" tablet. I need to be able to see two pages of music at a time (at least).