Rubinstein was born in Germany, and, after moving to the United States, started his artist career in the early 1970s as a teenager. Primarily working as an inker, his artwork has been published by major U.S. comics publishers including Marvel Comics, DC Comics and Dark Horse Comics. However, he first entered the industry as an office assistant to Neal Adams and Dick Giordano at Continuity Associates. While working this position, he learned how to ink from Giordano.
At age 17, he met Mike Nasser, who had just received his first comics assignment, penciling a backup feature in Kamandi #45-46. Nasser allowed Rubinstein to practice inking on photocopies of his pencils for the story, and afterward showed the results to editor Gerry Conway, who then assigned Rubinstein to inking the story. Rubinstein has complained that following this story, editors shoehorned him and Nasser as partners, pairing them with each other on every assignment.
In 1982, Rubinstein inked the acclaimed Wolverine limited series.
One of his most important works has been inking The Official Handbook of the Marvel Universe over a span of twenty years, for which he holds a Guinness World Record of inking more pencillers than any other inker. Rubinstein recounted,
I did an inker\’s round table for a magazine called Comics Scene, where Klaus Janson, Tom Palmer, Bob Layton and myself all inked a Mike Zeck drawing. Mark Gruenwald saw these and decide [sic] that mine was the clearest to understand what the character looked like, not necessarily the best inked, and when I came back from the San Diego con … Mark said, \”We\’re doing this encyclopedia, and we would like you to ink as many of the figures as you want.\” And I said, \”I\’ll ink all of them,\” which turned into a gold mine and a godsend. [laughs] And he picked me because he knew that I would not make a homogenous look of it, and I honestly think I chameleon my style enough…
Among his extensive inking credits (which include more than 2,500 comic books), were work with Michael Golden on Micronauts, Jim Starlin\’s Warlock and Aquaman with Don Newton. Later assignments included a mini-series for Dark Horse Comics called Archenemies, and co-inked issues of DC Comics\’s Ion mini-series and Green Arrow/Black Canary.