I have found many mangas and some novels about devilman and got confused about it and don't know where to start so can anyone help me about it.
Ok, if we are going to go into Devilman and the reading order for it, we have to get into semi-spoiler territory for the ending of the original manga, so you are gonna be warned.
Keep in mind this is predominantly for the manga, which forms the baseline you need to have to get into this series.
- Start with the original Devilman series, which ran for 5 volumes. The series ends, with a time loop, and I won't go into circumstances, but it is barely touched upon in the Netflix Crybaby Adapation.
- Shin Devilman is a side story that happens sometime in between the main series, before Akira is betrayed.
- Devilman Lady is a series that has to deal with fallout from the events of the original series timeloop and the aftermath of it, but that comes closer to the end of this storyline.
- Neo Devilman, Amon: The Darkside of Devilman, and Devilman: Strange Days are "what if" and side stories that pertain to OG, SHIN, and LADY storylines.
- Lastly, we have Demon Knight, which is a prequel to Devilman, and finally Devilman Saga, which partially concludes it.
Go Nagai's other series, Violence Jack, also has ties to Devilman as well, but I won't go into that.
Ultimately, the order would be OG, SHIN, LADY, SAGA, JACK. Everything else (Neo, Amon, Strange Days, Demon Knight) can be read later.
These answers were provided from my knowledge and a bit of fact checking from The Devilman Wikia