The battle in question took place during the Korean war, in March 1951 between the British (and Belgian) 29th Brigade and the Chinese army. 29 Bde were dug in on the mountains overlooking the Imjin river, north of Seoul and the Chinese Army mounted a "human wave" attack to force them off. The abiding story of the battle is the Gloster's gallant (but doomed) defence in the face of astonishingly overwelming numbers, but the Royal Ulster Rifles, Royal Northumberland Fusiliers, the Belgian Regiment, the 8th Hussars and the Royal Artillery all played a central role as well, facing similarly difficult conditions and standing up against the enemy with equal gallantry.
The book is *exceptionally* well written: it is supremely readable and, calling as it does on interviews with the survivors, it is by no means a dry historical account. It gives plenty of air time to all the participants (including the Koreans themselves) rather than simply focusing on the Glosters alone. It's worth noting that other accounts have tended to ignore the other units who fought in the battle (much to the annoyance of those concerned) which makes this particular treatment all the more important.
There is a fairly long exposition, discussing the cause of the war and its progress up till the battle itself. This puts the battle nicely in context and in no way detracts from the story.
This is a highly reccomended book about an epic event. Buy it!