This story finds Corto reuniting with many friends from previous stories, searching for the Mu, the fabled lost city. The Mu story is incredibly convoluted, making this a particularly hard translation. Lots of statements contradicting previous statements. It took me a while to come to the decision that Pratt was doing this on purpose, but the discovery of just what Mu turns out to be is a big part of the ongoing story.
This one is one of the longest Corto stories, and there are a lot of trippy dreams and dreamy trips that happen throughout. This is the loosest of Pratt's draftsmanship, and my favorite Corto Maltese art. The story meanders all over the place. The ending is in fact very affecting, especially if one has read some of the previous books (Corto Maltese in Siberia would be the key book there). --ECC blog
I liked the Mayan-style reference art and watercolor style here, but I don't recall if I've read the "Mu" story itself, as it's been a while since I dipped in to CM. Some more art samples from the story here:
https://www.google.com/search?q=%22corto+maltese%22+%22MU%22&udm=2
TBH I'm nowhere near the 'controlled-looseness' of Hugo Pratt's ink and watercolors, but I sent you a link, yeah.