I love both of their work, however I will make a disclaimer:
For those interested in "mentalism", their work looks INCREDIBLE. For those currently working to be 'mentalists', most of their work is daunting.
It's not the type of material you can just pick up and do. You'll be fooling yourself more than your audience. I'm not entirely sure how to put this into words, but for those who have made the journey in either magic or mentalism understand when I say; you'll come across material that everyone likes but very few people understand.
In card magic, Helder's work can be like this. Their work is incredibly powerful because of its potential to reach past being a "trick". So just be careful when selecting material like this, it takes a ton of work. If you haven't been involved in the study of magic and mentalism, this may be way over your head. If it seems simple, you might want to double check your level of understanding.