SumatraPDF is a very lightweight pdf reader, but can also open mobi e-books and other documents. But its the default font is not friendly to the e-book reading, therefore, this article provides e-books change the font size and other ways to improve the reading experience.
Setting method:
Open SumatraPDF reader, tap Menu> Settings> Advanced Options
Open a text configuration file with txt find EbookUI [.........],
replace
EbookUI [ FontName = Microsoft YaHei FontSize = 12 TextColor = #5f4b32 BackgroundColor = #fbf0d9 UseFixedPageUI = false WindowMargin = 2 4 2 4 PageSpacing = 4 4 ]