And as far as I'm concerned, there may not be an adaptation of Umineko Chiru considering how underwhelming the first season performed.
If you're gonna experience the story, the visual novel (the game, that is) is the way to go. The manga isn't even fully released yet; they just release each chapter simultaneously. But you really should start reading the VN from EP1 through EP4 before getting into Chiru, which starts at EP5. Trust me, it makes all that more of a difference.
There's a demo that can be downloaded for free, but it only goes as far as EP1 (which is covered in the first five episodes of the anime). The link I gave you also has links for you to actually download the full games, though it costs money. Remember, to get all the episodes, buy EP4 (which contains all the material shown in the anime from start to finish) and EP8 (which covers all of Chiru, which you haven't seen).
Also, you should know that the visual novel has been remade as a PS3 game, with more polished art and full voice acting. They're gonna do the same for Chiru, plus all the remakes are going to be released on the PSP.