I was grinding through Finnegans wake. Took ages! Dropped my book on the floor of the train one day and the bookmark fell out. Worst day of my life, I couldn't find out where I was up to and just gave up and stopped reading it.
That seems like a fine argument for writing in books--just flip forward until the marks run out. And actually, based on my own long-ago (and very brief) experience with FW, I can't imagine reading it without marking it up.