A number of individual titles in Ben Bova's
Grand Tour series are now down to just 99p at Amazon UK. Some of them only appear to have dropped in the last day or so - cheapest prices to date according to eReaderIQ.
Mars
Return to Mars
Saturn
Mercury
Titan
Venus
The Precipice: Asteroid Wars I
The Rock Rats: The Asteroid Wars II
The omnibus of
Mars,
Moonrise,
Moonwar, and
Return to Mars is still available for £1.93, as per the details in the
separate thread.