Black Jack is one of the best manga that you can find. It was made by Osamu Tezuka(The God of Manga) himself and is considered one of his best works. Here we have two short stories drawn by several different artists and not Tezuka himself. But believe me when I say that this manga does not fall short in any way.
If you have read Black Jack then you'll surely like it but in case you haven't still it'll be good a read. It manages to ooze out the same feel as the main manga. It is short- only two stories, so no reason to delay
Also, I recommend reading Black Jack itself if you like episodic manga and even if you don't. Every story is a masterpiece in itself.
Even in Black Jack Alive the characters stay true and interesting.