I love it!
In a nutshell, it is nothing but piano playing all the instruments (guitar, bass, and vocals) so its not any more complex than writing a midi score on your computer and playing it with that stupid comp synth effect. But the performer is really good and it just thrills me to hear clearly Iron Maiden music in its full complexity, without any guitar distortions, which have that effect to cut on tone's frequencies and make the melodies sound much "drier".
If you listened to these songs a thousand times already (like I did), and kindda got bored of them, but also like to sing along or reminisce a bit, you will love this too.