Length is the laziest proxy for seriousness. Some of the books that have rearranged the way I think are slim enough to read in a weekend, and the slimness is part of why they stuck. The author had to pick what mattered. These are short on purpose. A few are essays, a few are how-to, a couple are almost prose poems. None of them outstay their welcome, and all of them have a way of looping back into your week long after you have shelved them.