Definitely Moon+ Reader Pro. In some respects (for example, Themes treatment, ability to import your own background textures/photographs, etc.), it's even better than Marvin. Overall, Moon is weaker than Marvin, but certainly nothing to sneeze at – a very respectable piece of software. Communication with Moon's developer, a really nice Chinese guy, tends to be monosyllabic, and you likely won't ever find him on MobileRead, catering to his users like Kris, but he does try to do his best to be forthcoming. He once sent me the link to download an alternative Moon version when the official Play Store version broke something. Plus, Android as an operating system isn't quite as dumb as the indescribably dumb and user-limiting iOS (getting dumber and dumber with each annual release), which brings advantages to the user, also of e-reader software.
That said, if my only iPad broke (but I have 3 of 'em, just to be sure), I'd instantly shell out €250 or so for an older but still perfectly capable iPad mini 2, if only to be able to continue using Marvin.
In an ideal world, naturally, there would also be a Marvin for Android, Marvin for desktop Windows, Marvin for Linux, and Marvin for Mac OS, but that is, perhaps, an unattainable utopia.