I read that book recently and it triggered my interest in "the art of remembering".
Then I moved to "how to develop a perfect memory"[1]. It gives practical tips for remembering lists, numbers, appointments, faces.... It works surprisingly well. The thing is that nowadays, we usually use technology to remember those kind of things.
I think there's a huge difference in the types of contents that are "hackable" and the ones that have to be learnt by assimilation. I can remember 50 digits without any problem, but remembering subtle content from a book, how to use a new API,... it's much more difficult to find mnemonics for that in my experience.
Anyway, I think it's great fun to "hack" yourself to be more efficient, and this, along with speed reading and lucid dreaming could have exponential effects. I'm on it. on both. We'll see.
The author won the US Memory Championship after just a single year of learning and practicing mnemonic techniques.