cjleeh: Shazam! Sale, Up To 83% Off. Ends 4/29/19
https://www.comixology.com/Shazam-Sale/page/21198 It looks like "Shazam!: Origins" is a pretty good place to start if you never read his comics before. Which is the situation I am in actually. I was more of a fan of the DC animated movies he has been in, and never put much thought into reading the comic until now.
Be cautious of Shazam!: A Celebration of 75 Years. From what I have researched, and heard from reviews. It is not a very good representation of the history of Captain Marvel, or the entire story behind his origin. So I feel like it can be skipped in favor of something with content that you can read from beginning to end, and get a richer experience.
If I may share my opinion...
If you liked the film, then you should buy
Shazam!: Origins, because the film is heavily based on that comic, but it's the most modern version and changes a lot of core things about the character —I'm not saying this as a bad thing, mind you, just as a fact.
On the other hand, I would recommend buying
Shazam!: A celebration of 75 years before anything else. It gathers stories from all the different versions of the character (the original Captain Marvel when it was published by Fawcett Comics, and the three or four attempts DC Comics has launched since the 70s) and the good thing is that, if you buy it now, you have nearly a month to read it and decide which is the version you like the most.
Personally, if you want a kid-friendly comic, I would put my money on Jeff Smith's
Shazam! The Monster Society of Evil and the comic book series that followed it,
Billy Batson and the Magic of Shazam.
Then, If you liked the film, like a said before, your comic is
Shazam! Origins (but I wouldn't buy the new series, because only the issues one to four are on sale and nowadays DC Comics rarely put anything but Graphic Novels on sale, so next time you will have to pay full price for issues 5 and 6 or buy the graphic novel collecting them).
Last, but not least, if you want a modern approach but closer to the original Captain Marvel, I would buy
The Power of Shazam by Jerry Ordway. It's possibly one of the best takes on the character and you have the original graphic novel on sale and all the issues (1-47) of the regular series that followed up, including the annual from 1996. Sadly, there is only one missing comic, the 1 000 000 special issue.
Kingdom Come is a comic with Captain Marvel in it, but it's not a proper Captain Marvel comic. Anyway, it's a must-have for any reader.
The rest of the sale is also interesting, but I would recommended it only for hardcore fans:
Shazam! The New Beggining,
Convergence: Shazam!,
the Trials of Shazam! and
Superman / Shazam First Thunder! are good comics even if they didn't make a big impact on the long run. And then you have a lot of single issues from several series which I cannot really recommended and I'd only buy if I'm really interested in those.
The big thing missing from the sale is
The Multiversity: Thunderworld Adventures from 2014. A great comic by Grant Morrison and Cameron Stewart that can be read as a stand-alone issue starring a very funny and classic version of Captain Marvel with a modern approach
à la All-Star Superman.