Presumably you are looking for a good, free copy of the US Constitution and/or it's amendments. This is the one to get. It's all here in this one volume, and it's beautifully laid out, with nice artwork.
I started with the highest-ranked one titled 'The United States Constitution', with a cover that looks like a plain book. It lacks the Bill of Rights and the other amendments, and the layout is not polished. Then I tried two similar looking ones that are titled as being the amendments. They don't even contain the amendments. That's right: there are no amendments in the book titled, 'Amendments of the United States Constitution.' Worse, there are two of those with just slightly different names.
I had overlooked this one at first because it didn't have enough reviews yet to show a star rating, but that was a mistake. This one is great, with the entire constitution and all amendments is a single well-designed volume. This is the one you want.
This edition is really gorgeous — much better than the free iOS apps I have tried, which all seem to have ads or idealogically motivated commentaries attached.