document.body.style.fontFamily = "Baskerville";
Baskerville has a nice long-s. TNR is also not bad. Garamond is passable.
on edit: liked the Garamond better, since the font is a bit thicker, checked it on "ſpake" and was obviously a long S whereas on the thinner Baskerville still looked like an f to me. Although the original text was perhaps too thick for me.
on edit: this was probably where my problem generally was, in lest and Maister and anything where the long s is next to a t it looks very like an f to me, although if I zoom to 170% then it is clear, however at that size it introduces its own reading problems; unfortunately my reading glasses are broken so I just struggled at a lower resolution.