There are now 2 books. The first book named "Alvinus" features art from 2015 and was published at the end of 2015. The second book is named "Alvinus: TNTCL" features art from 2016-2020
Both artbooks feature art that is set in a universe where Elves are real, Giant rocks float carrying a city on its back and tentacles are a part of every day life.
If you are having trouble obtaining the book, Please get in touch!