Maybe a bit subjective but Fiko reading interface is cleaner and simpler than others plus it renders code blocks correctly compared to others. One of the leading reader Postlight does not render code blocks as code blocks. Other readers add a lot of cruft besides cleaning up the meat of the page.
I am not affiliated or anything with Fiko but I encourage you to give it a try.
I am happy to use any other if it has a good reading experience - choice of fonts, themes, export etc.