Michelle Magorian scooped the 2008 Costa Children's Book Award with Just Henry, a huge 700-page book that made me cry. Not many authors can do that but Magorian handles dangerously emotional stuff and pulls it off without slipping into mawkish sentimentality. Hence tears.

The same quality marked out Goodnight Mister Tom, her first novel, which won the 1980 Guardian children's book prize and has been read by every child in year 6 and many others both younger and older – rightly so – ever since. Goodnight Mister Tom is avowedly weepy. Only the hardest heart could remain unmoved. I once met a child who'd sticky-taped three pages together because they made her cry too much – I'm sure everyone who's read the book will know which three.

In Goodnight Mister Tom, Magorian had the external drama of the second world war as an emotional backdrop: put simply, there was a lot to weep over. In Just Henry, however, the setting is 1949 and there should be – and is – a feeling of optimism and hope. It is a period that's rarely used in fiction but Just Henry reveals it to be one that's worth exploring. The effect of the war is still being felt in the social changes it brought about. Life didn't just "slip back": few families were lucky enough to remain unaffected. Fathers were lost or altered; mothers found themselves raising families alone, or having to return abruptly to a subordinate role; children were forced to make adjustments either way.

In her big, bold novel, knitted together with more mysteries and coincidences than are credible, Magorian wonderfully captures that uncertainty and shows children's ability to move forward and embrace change far faster than their parents or grandparents. Lest this realism and the solving of the mysteries is too mundane, Michelle adds an extra layer of emotion by weaving in the stories of film stars from the movies of the day. For once, the current fashion of long, long, long books is justified. Just Henry is a wallowing great read. Just don't forget your hanky.