Paperbacks: Secret Knowledge<br/> A Writer at War <br/> Hans Holbein<br/> Swimming Underwater <br/> District and Circle <br/> Oxford Concise Dictionary of Quotations: Fifth Edition <br/> The Triumph of Numbers

Secret Knowledge, by David Hockney (THAMES & HUDSON £24.95 (328pp))

Hugely pleasurable to flip through, this gorgeous scrapbook of art advances Hockney's thesis that artists since 1500 have often used some form of optical projection to clarify the images they wish to create on paper or canvas. Through startling juxtapositions - a kitchen whisk drawn by Warhol alongside the sleeve of a garment by Ingres - Hockney notes the more confident appearance of a line that has been traced rather than "eyeballed". The greatest draughtsman in modern art notes how Caravaggio's technique progressively gained impact through his use of mirrors. Despite the astonishing verisimilitude of Holbein and Lotto, close examination of their works indicates varying vanishing points, which suggests the use of lenses. This new edition has been expanded to include Hockney's exploration of the camera obscura. A hilarious photograph shows the artist as a bulge under a black cloth outside a stately home while trying to recreate an architectural drawing by Repton. Hockney ruefully admits one drawback to the technique: "Then the heavens opened..." In the catalogue for his current exhibition he explains: "The camera sees geometrically - we must see psychologically." CH

A Writer at War, by Vassily Grossman (PIMLICO £8.99 (378pp))

Edited by Antony Beevor, these notebooks by the author of the epic novel Life & Fate convey the horror of the eastern front with unparalleled vividness. This book is dominated by Stalingrad, described with a terse precision that would be envied by any poet. The smell of the front line is "a cross between a morgue and a blacksmith's", while aircraft make the sky "hum night and day, as if we were sitting under the span of a huge bridge". Atrocity reaches its apogee in Grossman's account of Treblinka. Despite attempted suppression by the KGB in the Sixties, this classic of war journalism survived on microfilm. CH

Hans Holbein, by Derek Wilson (PIMLICO £12.99 (302pp))

It is a chilling irony that several of Holbein's subjects who had their lives cut short by the executioner's axe continue to live through his radiant portraits. Promoted as "an excellent artist" by Erasmus, Holbein would have been significant at any time, but the tempestuous nature of his era adds an additional resonance. This fine biography unpicks the coded messages in Holbein's paintings, such as minor differences in the two versions of Household of Thomas Moore that indicate the prelate's fall. Wilson depicts Holbein as a feeling, if "self-contained", man, who "gave visual expression to Protestant humanism" during eight productive years in London. CH

The Triumph of Numbers, by I B Cohen (NORTON £9.99 (209pp))

This valedictory volume from the Harvard historian of science is a lively exploration of the significance of numbers to humanity. Statistical competence was vital for the pyramids, whose blocks arrived at two-minute intervals, and 17th-century insurance companies. Florence Nightingale used her "passion for statistics" as a lever to move governments, but Dickens characterised the Victorian love of enumeration in the form of Mr Ledbrain, who devoted his energies to calculating the number of skewers of dog meat sold in London per annum. CP

Oxford Concise Dictionary of Quotations: Fifth Edition (OUP £9.99 (580pp))

Anyone needing instant education could do worse than read this brisk reduction of the world's knowledge, as long as they can read it (the print is tiny). They will learn that great minds think alike. Julian Barnes: "Books say: she did this because. Life says: she did this." Ezra Pound: "Literature is news that STAYS NEWS." They will also discover that great humour stays funny (Byron on Coleridge: "Explaining metaphysics to the nation - I wish he would explain his explanation") and even that "Happiness is a cigar called Hamlet", though this is not indexed under "happiness" or "Hamlet". CH

District and Circle, by Seamus Heaney (FABER £8.99 (76pp))

Forty years after the publication of his first collection, Heaney continues to plough the furrow of his native landscape. In a collection packed with generous tributes to friends, old and new, literary and rural, he also muses on love and death in a time of terror - the fact that "Anything can happen, the tallest towers/ Be overturned". Poetry just doesn't get much better than this. CP

Swimming Underwater, by Sheena Joughin (BLACK SWAN £6.99 (316pp))

While her friend Clare dies, her book about poets dawdles and her scattily artistic family and friends tie themselves in knots of dreams and regrets, Ruth drifts through a West London (with trips in time to Leeds and Paris) that glows with a scuzzy glamour. Joughin's second novel confirms her gift for mining tragi-comic gems from the outposts of shabby bohemia. The poetry adds poignancy, not posiness: more Larkin than Plath. BT

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