The Enter the Gungeon Digital Comic isn't worth your time or money, unfortunately. Oh, it's well enough drawn and colored, but it basically has no story; the vast majority simply depicts two characters' run through the Gungeon, which is completely uninteresting to anyone who has played the game—hell, it's probably uninteresting to anyone who hasn't, too. Nothing unusual happens to them, so what you get is just their reactions to typical Gungeon stuff as first-timers, and they aren't good enough characters to make that entertaining.
There's just no point to this, and it's a shame because Enter the Gungeon constantly hints at a colorful and fun wider universe through its lore text and NPCs. That wider universe makes an appearance in this comic for about five of its pages, and it's not a terribly interesting portrayal while it lasts.
Currently, the only way to acquire this seems to be through the Collector's Edition of the game, and I would advise you not to consider it a significant reason to make that purchase.
This review can also be viewed and rated on Steam.