These days, nothing says amateur hour quite like an alphabetical bookshelf. From lifestyle magazines to design blogs (admittedly a short distance), there are limitless suggestions for how you should treat your books. You can arrange them by genre, by time period, by size or by color (all well and good until you realize how strangely few books have purple spines). You can stack them in height order. You can angle them across the wall in gentle waves of Swedish manufacture. My own system of classification is one of emotional practicality.