Here is a 'Nova' post about an app rather than a book, but it is an app that can help you concentrate on reading books, or writing sermons, or planning the preaching for the next year, or anything else you do on your computer. It may be that I am the only person who gets distracted by the Internet while trying to work, but just in case, this might be useful. I have found the app 'Freedom' enormously effective. It allows you to programme periods of time when you are locked out of specific websites. It has ready-made lists and you can add or remove your own favourite distractions. People sometimes say that we should learn self-control and not need such helps, but that seems to me like saying an alcoholic should learn to frequent pubs. Maybe the day will come when he can, but in the mean time it is best for him simply to stay away. That is his exercise of self-control. It is not spiritual maturity to place ourselves within temptation's reach, rather the opposite in fact. Freedom is also comparatively cheap, at just a few dollars a month. You can find more about it here: https://freedom.to/why?utm_source=frdmblgtop.