Serif v Sans Serif for print media
He pointed me to Kevin Connolly's thesis at the University of Calgary on legibility: "Legibility and Readability of Small Print: Effects of Font, Observer Age and Spatial Vision" (1998).
I also found Kathleen Yoshida's workshop on 'Avoiding Font Fiascos' (pdf) which contained some useful exercises on legibility to work through for the reader's own understanding.
It seems the popular jury is out on whether serif or sans serif fonts are easier to read in long bursts. But I still hold to the 'old rule' that long text is less tiring on the eye with a serif font than a sans serif. Of course, it depends on the font you are using (a really complex serif font is more difficult to read than a simple sans serif) but if one sticks to the time-old, boring fonts like Times Roman then one can't go wrong.
And I've been reading FontLeech and Typomancy blogs - very interesting reading if you have a secret love of fonts (as I do)