I was editing a book I received a while ago and ran into a puzzle when trying to figure out who the publisher was. The book is THE GARDEN CLERK'S DICTIONARY, ISBN 0976520605. Inside the front cover it says it was published by Dan Heims, who is also the editor and illustrator. Below that it says it was printed by Apollo Graphics (which Amazon has as the publisher) and on the back cover it has, under the ISBN, hortmedia.

So which one is the publisher, or should all three be listed as publisher?

Both Barnes and Noble and goodreads say that the publisher is Hortmedia.

I'm seeing lots of listings for Apollo Graphics as the publisher, but Hortmedia would be fine, too.  You'd only need one.  I'd  list Dan Heims as the editor, since IMHO that's his most important role here.  In the author box you'd list him as

Dan Heims (Editor)