Mobi or HTML or .lit or PDF--which file type do I need for my eBooks?

You’ve narrowed down which titles you wish to purchase from TWRP’s eBook store, now which format is best? What do the different format file types mean and where do they each work the best? Why are there so many choices?

The International Digital Publishing Forum describes the goal of Open Publication Structure (OPS) as “to define a standard means of content description for use by purveyors of electronic books (publishers, agents, authors et al.) allowing such content to be provided to multiple Reading Systems and to insure maximum presentational equivalence across Reading Systems.” In other words, the industry is attempting to set a standard format to make downloading and keeping eBooks easier. According to Mobipocket’s website, Mobipocket is one of the three main ebook formats based on the Open E-book Publication (OEP) formats, a precursor to (OPS). But several file extension names are out there. Here are four we use at TWRP:

MS Reader (.lit)
Microsoft eBook Reader format. Can be used on desktop or laptop PC, Tablet PC and UMPC, or using Microsoft Reader for Windows Mobile. Microsoft’s website says eBooks are also readable on “some new Windows CE consumer devices coming to market.” As of March 2010, Microsoft does not plan to make this format available on Macintosh, Palm, or Linux, and considers .lit to be proprietary—not available to eBook readers that do not support MS Reader. In this non-OPS format, digital rights management (DRM) allows all eBooks in MS Reader to be read on up to four devices. Mobile devices listed as “Windows Powered” generally ship with MS Reader installed, or you can download it free from Microsoft.

Web (.HTML)
This as another OEP format, and means “hypertext markup language.” Any web browser should allow viewing of this format. Readers such as Mobipocket and Kindle use HTML files in a compressed form within their file types, and HTML format can be converted for use on the Kindle. This format does not offer DRM support, where .mobi, .pdf, and .lit do. Files in HTML are often large and require lots of storage space.

HTML can be read on the following eBook devices: Apple iPad; Azbooka WISEreader; Bookeen Cybook Gen3, Opus; COOL-ER Classic; Hanlin e-Reader V3; Hanvon WISEreader; Nokia N900; Onyx Boox 60; Pocketbook 301 Plus, 302, 360°; Viewsonic VEB612

Adobe (.pdf)
Portable document format (.pdf) is an OEP format best viewed on a full-sized screen such as on a PC or Mac. Of .pdf format, Microsoft says, “PDF is a great format for capturing documents and print images. However, it is static and does not scale well, or change to fit the size of the screen you're using, which introduces limitations.” For the fixed-image file to be viewable on a handheld device the file has to have been created with a special reflow code; locked files such as eBooks will not allow this reflow to be added later. On a computer, you will need Adobe software to view a .pdf eBook, such as Acrobat or Reader. Adobe Reader is available as a free download from Adobe.com

That said, .pdf is supported by the following eBook readers: Amazon Kindle 1, 2, International, & DX; Apple iPad; Barnes & Noble Nook; Bookeen Cybook Gen3, Foxit eSlick; Opus; COOL-ER Classic; Hanlin e-Reader V3; Hanvon WISEreader; iRex iLiad; iRex DR1000; Iriver Story; Nokia N900; NUUTbook 2; Onyx Boox 60; Pocketbook 301 Plus, 302, 360°; Sony Reader; Viewsonic VEB612 (The only hardware claiming not to support PDF is the Azbooka WISEreader).

Mobipocket (.mobi)
Mobipocket is software designed to catalogue and display ebooks on many devices in .mobi format. You can download Mobipocket eBook Reader for free to a windows-based PC, then link your PDA, smartphone, or Blackberry via USB to transfer titles to your handheld device. Mobi files are accessible to Apple computer systems running Mac OS X 10.2 or later. Amazon has also released a Linux-compatible Kindle file generator.

Mobi is supported by the following eBook reader hardware: Amazon Kindle 2, DX; Azbooka WISEreader; Bookeen Cybook Gen3, Endless Ideas BeBook; Opus; COOL-ER Classic; Hanlin e-Reader V3; iRex iLiad; iRex DR1000; Nokia N900; Onyx Boox 60; Pocketbook 301 Plus, 302, 360°; Viewsonic VEB612

So why choose .mobi over the other three formats? “In a nutshell,” says RJ Morris, Owner & Executive Administrator for TWRP, “Mobi is a format that is suited to the latest in ereaders, the famed KINDLE. It allows a handheld of that kind to resize the text, where as a .pdf is limited, since it is seen as an image rather than text. Not all ereaders can take the Mobi format, but it adds to the selection for our customers.”