You are correct. The site does not offer download or ebooks.
When you "rent": the book will appear in your Reading List and you'll have access to the book for 7days. For example looks like this -> for Amber By Night http://twitpic.com/4farpy
(it'll have a time clock next, indicating how much time you have left)
When you "keep": the book will stay in your Reading List. The book doesn't expire.
We built this site 8 years ago and the idea behind emanga, back then, was "try before you buy" - "try reading online, before you go out and spend $12.95" Now, times are changing- people are looking for ebooks and other digital format.
With DMG (Digital Manga Guild - www.digitalmangaguild.com
) launching in April, Our IT/development staff is working hard to upgrade this site; new features will be available in summer and we are trying to make this site more user friendly. We are planning on eliminating the "points" system too and will be replaced by $-dollar amount, like you mentioned.
I can understand why you think there isn't a merit on renting and not being able to download. One of the great thing about eManga.com is that it's made accessible from anywhere in the world with internet access and also without having to purchase expensive hand-held devices.