I have a Kobo E-Reader and where possible I try to get books in epub format. There have been two problems, the first that many Buddhist books aren't available in epub. I can't do much about that. The second is that Sankrit words in many books use the standard diacrits when transliterating and these are not included in the standard fonts bundled with the Kobo. I have a solution to the second problem. You can add fonts to the Kobo by creating a fonts directory and putting true type font files (ttf) in it, SIL has a font named Gentium Plus. You can download them from the SIL International
site, connect your Kobo by usb to your computer, create a fonts directory, and copy the two ttf files into it. After you disconnect the Kobo, you can select the Gentium font and the missing letters with diacrits will show.