Sometimes for really dense/cerebral stuff (especially stuff that needs supplemental charts/references) it can be tough/pointless, same with slower/less engaging fiction. WWI history book took a few rewinds, Had to re-read GoT 5 on the elliptical (read the other 4 no problem when I was epic commuting). Made it through The Selfish Gene like it was nothing though. I've read a huge pile of old sci-fi (including really dry shit like Clark and Azimov) while doing everything from my job, to driving, to mowing. Read about 75% of Mein Kampf on the lawn mower, read The Turner Diaries while VR space trucking...