Tsuruta's rough-looking art is absolutely beautiful, and more than makes up for the slow and sometimes complete lack of story. Buy the physical release to get the best experience!
This series feels like a cross between two Ghibli movies: It has the biplane-flying ocean setting of Porco Rosso, and a mysterious, legendary island like in Laputa: Castle in the Sky. Going a little further with this comparison, I could say it has the laid-back, almost whimsical attitude of Porco Rosso and the sense of wonder and imagination that drives Laputa.
These are the things that made me read and later buy a physical volume of
Wandering Island, but the best asset of this series is the art. I don't want to sound like an advertisement, but I really want to stress how good the art looks in the physical volume (I got the U.S. Dark Horse volume - it's really high quality!). The manga mostly sticks to within the borders of the panels, and then, as I flip the page... the art EXPLODES out of the panels, spilling out to the very edge of the page in a huge 2-page spread. I never really noticed that when reading the scans, and I can't get over how such a simple thing could have so much impact.
Anyway, Tsuruta has a rough style that always looks hand-drawn. If you look closely, some lines are kinda crooked, making things like fingers and clothes look funky, but it always looks great when put together. The character design of the main character and really the whole thing looks a little like it's from Blade of the Immortal. In contrast to that, though, the story is really slow, to the point where some chapters have almost no dialogue at all - just panel after panel of Tsuruta flexing his artistic skill.
Check this out if you're looking for a slower seinen series like YKK or Aria, and definitely consider buying the physical release! It's well worth the money.