It may also have been remaindered because it's not an exciting book. It's perfectly well-written but it's not much more than a solid military history of the three years 1918 - 20 narrating what happened on each of the (many) fronts between Bolshevik and White forces. There is no attempt to convey the feel of those years - the cruelty, the suffering, the sheer carelessness of human life - much of it simply continuing the story of World War One but now with civilians rather than uniformed soldiers as principal victims.
In his Conclusion, Mawdsley (a Professor of History at Glasgow University) devotes a few pages to totalling up the deaths and injuries. Whenever you see a figure which says that soldiers were more likely to die of disease than wounds then you know are you looking at a conflict in which it was nightmarish to be involved.
The book has some use as a work of reference but since it is so much concerned with dates, it really should have included a time line Chronology as a separate Appendix.
As for Mawdsley's judgements, I found most interesting the idea (picked up from Roy Medvedev) that had the Bolsheviks not introduced their Maximalist programme, but instead adopted something like the 1921 New Economic Policy back in 1918 and at the same time accepted the strength of the SRs [Socialist Revolutionaries] in rural areas, then they could have secured overwhelming popular support and much reduced the miseries of both the Civil War and of War Communism.