KRJRS, to elaborate in broad terms:
HTML, RTF, and DOC are document formats. They exist to store/archive information in readily editable format. HTML has also been used as a publishing mediumm on the World-Wide-Web but thatwas not its designed intent which has led to a lot of issues and debates over the years. At its core, it still remains a lightweight version of SGML. XML, on the other hand was conceived and designed as an online publishing format which why most true ebook formats are based on it.
PDF and DJVU are electronic paper formats, essentially digital microfiche in concept. They store information with (generally) hard-wired, frozen formatting. Editing them is not a (generally) supported feature, printing mostly is.
FB2, ePub, LIT, eReader, docReader PDB, and Mobipocket are ebook formats. Intended for reading, not editing or printing. (Some) formatting is embedded but is not (generally) intended to be hardwired; reflow and end-user formatting are expected to overide the internal controls at render time.
An ebook is not the same same or as etext or an edocument or epaper; it is intended to be a mass publishing medium, not an archival medium, which is why most ebook formats are built off XML and other web standards. Some people do speak of documents in those alternate formats as "ebooks" but they are out of line with current usage and only muddying the waters which can lead to unfortunate confusion for those that don't fully research the subject.
As of today, the two dominant ebook formats are Amazon's Mobipocket format (thanks to consumer-level market share) and ePub (the annointed universal standard of all the major publishing houses) as implemented and interpreted by Adobe ADE. FB2 is a solid number three overall and regionally dominant for DRM-free publishing. LIT, docReader pdb, and eReader are still actively supported by many publishers and second-tier online bookstores (both with and without DRM) but they appear to be falling back into the ranks of legacy formats. That may change; Barnes and Noble, the current owner of eReader is still selling content using the format which is supported by the Nook and Jetbook lite ebook readers, and there are rumors that Microsoft is not giving up on LIT. But for now the bulk of ebook readers are built for either ePub or Mobi first and everything else second or third. Many go no further.
Modern ebook readers are intended for reading ebook formats. That they support non-ebook formats at all is a *bonus* feature above and beyond core requirements. The design parameters are skewed towards clarity of display, simplicity of use, and extreme battery life, not performance nor PC or PDA-like capabilities. Many are also handheld storefronts directly leading to online bookstores. They are NOT intended for hobbyists or corporate usage (like the Bother); they are intended for consumers of commercially published books (mostly fiction). To expect anything else is to be out of touch with the *commercial* reality of where the industry is headed. Sorry, but that is where the money lies.
As Marion Zimmer Bradley said "The world goes where it will not where we wish it to go." (more or less.
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Published content, not documents is what ebook readers are for.
Document readers are a separate product category (Brother has the most prominent one:
http://japantechniche.com/2009/03/13...iewer-sv-100b/) that shares some traits with ebook readers.
Given the stated use pattern and desires, I have to agree that the Viliv would have, in fact, been a better tool for the mission. They are wonderful pocketable COMPUTERS and make decent ebook readers, though that is not what they are designed for.
The good news is that it should not be at all hard to find somebody looking for an ebook reader, not a pocket computer, and willing to buy a slightly used PB360.
Good luck finding a new home for your PB360.