Books might only give us an insight but the experience can still change when we are on the real scene already, especially for something that is unstable like the crypto market. By being aware of it, it can automatically tell us that a stable profit seems kinda hard to achieve. A regular profit is still possible though, same goes with winning in the long term but that is if we already grasp things. He said he read 'some' books, so that can mean that he already explored other areas but it may not be enough yet or he still miss the other, so he will need to keep on moving.
One big downside with books is that not everything is that great when it comes to staying relevant for a long time. Sure there are some books about politics that was written during roman empire time that is still true today, aurelius or cicero wrote awesome stuff about politics that you can use even today, because politics is politics and there aren't really that much of a change on the long run, it's something we can always deal with and need to learn more about as well.
I believe that we are going to have some issues on the long run if we look at crypto trading related books though, because that is not something that can stay relevant and true for that long, not even for a full decade, it would be a totally different result after a few years.