The first comic book appearance of Boba Fett is not as quickly determined as one might think. It all depends on your definitions of "first," "comic book," "appearance," and even "Boba Fett." Settle down as we get sucked into a Sarlaac Pit of controversy over this one.
Now Boba Fett first appeared in the movie The Empire Strikes Back, as one of several bounty hunters, the one who took the carbonised body of Han Solo with him, to crime boss Jabba The Hutt. But in comics? Well, the comic book adaptation of The Empire Strikes Back appeared in a number of publications. Written by Archie Goodwin, drawn by Al Williamson and Carlos Garzon, coloured by Glynis Wein, lettered by Rick Veitch of all people, with Jim Shooter as EIC. The serialisation ran in Marvel Comics' Star Wars #39 to #44, with Boba Fett appearing in Star Wars #42 – and on the cover as well. Then there was that story formatted into a magazine size, called Marvel Super Special #16, a treasury-sized Marvel Special Edition #2: The Empire Strikes Back, and the paperback Marvel Comics Illustrated version. And that's just the ones published in the USA.
Star Wars #42 was published by Marvel in the US in September 1980, with Boba Fett on the cover, reflecting his popularity in the already-released movie. But the other three previous versions were published in the Spring of 1980 alongside the release of the movie, but none had Boba Fett on the cover. With the Marvel Illustrated paperback version of the Empire Strikes Back published first in May 1980, with artwork that would later be changed, showing a more gnome-like Yoda closer to the character's sketches than the muppet used in the movie. The art would be changed for subsequent printings when someone realised it didn't match the movie.
Also worth noting is the UK weekly comic book Star Wars Weekly published by Marvel UK which had changed its name to The Empire Strikes Back. The Empire Strikes Back Weekly #129 contained the last third of the American Star Wars #42 which featured Boba Fett, with a Boba Fett cover, but came out in August 1980, a month before it would be published in the US. While the first appearance of Boba Fett in the UK comic came in the opening splash page of The Empire Strikes Back Weekly #127 from July 1980.
But what has the marketplace decided? Well, they are all in for the later first appearance of Boba Fett with Star Wars #42 in CGC 9.6 grade selling copies between $1300 and $1600 in recent months. A 9.6 slabbed copy of Marvel Super Special #16 sold for around $1200. Empire Strikes Back Weekly #129 CGC slabbed at 9.0 recently sold for $610. while Empire Strikes Back Weekly #127 graded at 7.0 sold for $470.
But the actual first printing of the comic in paperback format? Marvel Comics Illustrated: The Empire Strikes Back? Just $45 on eBay recently. Too thick to slab, you see. Copies are going for a lot less on Amazon as well. If you were a collector looking to the Boba Fett long term, that's where I might concentrate and wait for the market to catch up.
Then of course there are the appearances in the newspaper cartoon strips, but that's a whole other can of Hoth ice worms to open…