[nickredding]

Kindle Fire uses the EXTH[501] field to decide if the newsreader should be used for a document. At present calibre doesn't set that for recipe output at all, so recipe output is viewed by Kindle Fire as a book. To get the (much nicer) newsreader calibre has to set EXTH[501]='NWPR'. This will also cause the document to be placed in the "Newsstand" tab on the home page of the Fire.

There are two places where this should be set--in mobi/writer.py and mobi/writer2/main.py. (The code seems to have been reorganized since I last worked on it so I'm unclear as to whether the tweak new_mobi_writer is still relevant.)

In mobi/writer.py, replace lines 1578-1583 with

        # Write cdetype
        if not self.opts.mobi_periodical:
            data = 'EBOK'
            exth.write(pack('>II', 501, len(data)+8))
            exth.write(data)
            nrecs += 1
        else: # fix for Kindle Fire--use newsreader for this
            data = 'NWPR'
            exth.write(pack('>II', 501, len(data)+8))
            exth.write(data)
            nrecs += 1

In mobi/writer2/main.py, replace lines 537-547 with

        # Write cdetype
        if not self.is_periodical and not self.opts.share_not_sync:
            exth.write(pack(b'>II', 501, 12))
            exth.write(b'EBOK')
            nrecs += 1
        elif self.is_periodical:
            # fix for Kindle Fire--use newsreader for this
            exth.write(pack(b'>II', 501, 12))
            exth.write(b'NWPR')

The Fire newsreader is obviously derived from the Kindle Android newsreader, but it's interesting to note the latter doesn't require the EXTH[501] to be set. It looks like Kindle Fire is using the EXTH[501] to categorize documents, and then decides how to display them based on the category rather than looking at the MOBI type.