There are thousands of iPhone apps for little one-off functions that seem silly until you actually use them. For instance, I have an app from Intelligentsia Coffee that has instructions for different brewing methods plus a timer. Now this might seem redundant; why would you need an app when you could just memorize the instructions and look at a clock? But now that I've started using it, I don't know what I did without it, and I'm convinced my French press technique is better. Yes, 13-year-old me would beat up current me too.
ReadMore seems like another one of those apps that fit a need you never knew you had. It's basically a reading log with a timer, so you can figure out how long it will take you to read a book and decide what to read next. You time your reading sessions, and as the records become more accurate it can tell you exactly how long until you finish a book. Then you can also input the page count from your to-read pile to see how long a new book should take. Yes of course you probably already know this if you read a lot, and I don't think it takes complexity into account (maybe that's a cool feature, adding a DFW vs romance novel switch). But still, genius right? It costs just $2 in the app store.