I've received quite a few questions recently about the firmness of our leather notebooks, and how to make them softer.
The leather I use starts out quite firm but will relax and soften over time, especially with frequent use. You can accelerate that process somewhat by conditioning the leather more frequently than usual (monthly is probably plenty to get that started). You can see a video about how to do that here. Other than that, just use your notebook and that will help a lot!
One thing to keep in mind, though, is that various kinds of leather differ in texture and pliability. Some leathers are very soft and others are firm, even when thoroughly broken in, usually due to the type of tanning and processing used. You can see more info on leather types here.