The iPad is the most open for reading ebooks of any device, except a laptop.... below is a list of formats and the app to read them on the iPad.... I got this from mobileread.com
iBooks (Fairplay ePub)
iBooks
Kindle (various formats)
[ame="http://www.
amazon.com/kindle-store-ebooks-newspapers-blogs/b/ref=topnav_storetab_kinh?ie=UTF8&node=133141011"]Kindle App[/ame], by
Amazon (iPad and iPhone apps available, no sideloading)
Barnes and Noble (Adobe Ignoble PDF and ePub)
Barnes and Noble eReader Apps, by Barnes and Noble (iPad and iPhone apps available, no sideloading)
Adobe Inept (PDF and ePub)
Kobo, by Kobo (iPad and iPhone apps available, no sideloading)
Txtr, by Txtr (iPhone app available)
Non-DRM Formats:
ePub
iBooks, by Apple (iPad app available now, iPhone app 6/21)
Stanza App, by Lexcycle (iPad and iPhone apps available)
IBIS Reader, by Threepress (HTML5 based, no app required)
PDF
Stanza, by Lexcycle (iPad and iPhone apps available)
Cloudreaders by Cloudreaders
GoodReader by Good-i-Ware
iBooks, by Apple (for both iPad and iPhone on 6/21)
Mobi
Stanza, by Lexcycle (iPad and iPhone apps available)
PDB
iSilo by iSilo (iPad and iPhone apps available)
Stanza, by Lexcycle (iPad and iPhone apps available)
Other:
Comics (CBR, CBZ)
Stanza, by Lexcycle (iPad and iPhone apps available)
Cloudreaders by Cloudreaders
http://itunes.apple.com/us/app/comic...=8] Comic Zeal by bitolithic.