These are different stories involving Devilman's world. Some are about Devilman and add to the mythology some are separate stories that don't involve Devilman but take place the same time as the events in the original Devilman manga. They are illustrated by various artists. There are some color pages in the start middle and toward the end. There are some truly amazing art and stories in these volumes.

Number one is written and illustrated by Lazy Hagawari, Tatsuya Egawa, Katsuya Terada, Ken Ishikawa, Go Nagai and Shinichi Hiromoto.

Number two is written and illustrated by Hitoshi Iwaaki, Noriko Nagano, Go Nagai, Akihiko Takadera and Kazuko Yumeno.

Number three is written and illustrated by Noburu Miyama, Miki Toro, Shinobu Kaze, Sho-u Tajima, Masaomi Kanzaki, Yoshikazu Yasuhiko and Iou Kuroda.

A tribute anthology for Mushishi.

Nina, a wyndian princess, and her guardian Cray are searching everywhere for Nina's missing elder sister, Elina. While traveling to her last known whereabouts they suffer an accident. On her way to a nearby town, Nina meets Ryu, a seemingly amnesiac young man. This meeting triggers a series of events that will involve them with the godly race known as The Endless, immortal dragons with the power to shape the world itself.
(Source: MU)

From Viz:
The trouble and fun began when ordinary teenager Tenchi Masaki inadvertently released the legendary demon Ryoko from his grandfather's shrine. Turned out Ryoko was actually a marooned space pirate! Since then, she's become Tenchi's unwanted houseguest, attracting a host of other troublemaking alien women: Ayeka, a haughty alien pricess; Sasami, her mischievous little sister; and Washu, Ryoko's mad-scientist "mother." Add Ryo-oh-Ki, an adorable little carrot-eating spaceship, and you've got one full Shinto shrine!

Kasche may have a talent for controlling beasts, but she's got a lot to learn about self-control before she can become a full-fledged summoner. When disaster strikes, her principal chooses her to avert it. Joined by an unusual crew of allies both human and not, Kasche must recapture the relic from an evil summoner before he can use it to unlock the ancient Encyclopedia Verum and call up the most powerful monsters ever seen!