Is this spondulix I see before me?

These two books epitomise the Janus-faced nature of modern Shakespeare studies. One fastens its gaze on the past, seeking the secret of Shakespeare's art in a deeper knowledge of his life and times. The other is transfixed by the impact of that art on subsequent cultures, by what we have made of it rather than by what it was made from. Both approaches illuminate aspects of the man and his work. But neither succeeds in shedding light on the central mystery - why his words hold the world in thrall four centuries after his death.

In Search of Shakespeare radiates the same enthusiasm its author displayed when he fronted the TV series that hatched it. Michael Wood's fascination for the look, feel, sound and smell of Shakespeare's Stratford and London is infectious, and his gift for imprinting them on our imaginations undeniable. His evocation of Shakespeare's rural childhood is embedded in the material reality of the Elizabethan household, with its painted wall cloths, bolsters, joint-stools, querns and skillets. Equally compelling is Wood's re-creation of the neighbourhoods Shakespeare lived in while he plied his trade on the London stage: the bustle of Bishopsgate, whose inns served ales called "huffecap" and "dragon's milk"; the surgeons, musicians, goldsmiths and scriveners he rubbed shoulders with when he lodged with the Mountjoy family in Silver Street.

For its expert restoration of "the human roar of a great pre-modern city", this superbly illustrated book takes some beating. But Wood is just as adept at reconstructing the less tangible factors that forged his subject's unfathomable personality. Chief among these is the closet Catholicism of Shakespeare's family, for which Wood makes a persuasive case. The evidence he marshals makes it plain that the Bard's kith and kin were riddled with incorrigible recusants: both his father, John, and his elder daughter, Susanna, fell foul of the church authorities for refusing to conform.

Whether Shakespeare himself "dyed a papist", as one 17th-century clergyman swore he did, is another matter. In 1613, a few years before his death, he purchased a property next to the Blackfriars theatre that was known to the government's thought police as a Catholic safe house, where mass was said in secret. But, as Wood stresses, suggestive though such facts are, they afford no proof that Shakespeare cleaved to the Old Faith, and no basis for imputing cryptic Catholic sentiments to his plays and poetry. That said, it is hard not to discern a direct connection between the climate of state terror he grew up in and his choice of a career in which self-concealment and role-playing were de rigueur .

Before Shakespeare was out of his teens he knew what it meant to live at the mercy of spies and informers in a family tainted by treason. The sight of the tarred head of his kinsman, Edward Arden, spiked on London Bridge would have made the cost of conscience all too clear. Wood argues convincingly that Shakespeare's assaults on institutional injustice and oppression in his history plays and tragedies have their roots in his intimacy with their effects. Add to that his acute class-consciousness as an "upstart crow" from the sticks and his empathy for the likes of Shylock, Othello and Caliban takes as little explaining as his passion for cutting kings down to size.

Wood offers plausible, though familiar, solutions to the conundrums that any life of the Bard must tackle. He plumps for William Herbert as the dedicatee of the sonnets, "Mr W. H.", and for Emilia Lanier, the first woman in England to publish a volume of poetry, as their infamous Dark Lady. As a guide through "the realm of diverting speculation rather than verifiable fact" to which, as he admits, such puzzles belong, Wood proves more reliable than most of his recent precursors. It is only when he enters the realm of the plays and poems themselves that he leads us seriously astray.

Sometimes this is the result of repressing his own qualms about reading autobiography into the art, as when he diagnoses the poet's crush on a youth in the sonnets as "a kind of transference" after the death of his son Hamnet. But more often it springs from fundamental misconceptions of Shakespeare's major works. Thus The Merchant of Venice is dubbed a failure because it "leaves behind an uneasy edge, a sense of unresolved tension", which is precisely the point of the play. As for Macbeth , Wood bafflingly concludes, "great as some of the writing is, the play, lacking parallel plots, is thin compared with others of the period". As it happens, none of Shakespeare's great tragedies has a parallel plot (let alone several) apart from King Lear , whose pagan nihilism Wood mistakes for a Christian "miracle play".

In Search of Shakespeare is marred, moreover, by enough errors to ruffle one's faith in its accuracy. The "Ill May Day" on which Thomas More addressed an anti-immigrant mob was in 1517, not 1511. If Ben Jonson lampooned his rival Shakespeare, it was as Lovewit in The Alchemist, not "Lovewhit in Volpone". The awesome speech in Measure for Measure beginning "Be absolute for death" is delivered by the duke, not Claudio. And it is the tale of Gloucester, not the tale of Lear, that Shakespeare lifted from Philip Sidney's Arcadia . It is, however, a measure of the book's quality that such gaffes count for little when set beside its achievement of igniting popular interest in Shakespeare's life and times.

John O'Connor's Shakespearean Afterlives is also pitched at a popular audience, but often much lower than it need be. Its aim is to track ten of Shakespeare's most enduring characters through myriad offshoots and adaptations of the plays down to the present day. Romeo and Juliet, Henry V, Cleopatra, Shylock, Richard III, Lady Macbeth, Hamlet, Prospero and Kate in The Taming of the Shrew have been reincarnated not only on stage and screen, but also in everything from opera, ballet and painting to cartoons, adverts and tabloid headlines. The last predictably billed Diana Ingram, the wife of the major caught cheating on Who Wants to Be a Millionaire? , as Lady Macbeth. That the chapter devoted to Macbeth's missus kicks off with that fact is symptomatic of O'Connor's anxiety not to be thought "narrowly academic".

On that score at least, he need have no fear. The book is Shakespeare Lite, and none the worse for that, if one accepts it as "nothing more than a series of personal reflections". The author's star-struck indulgence of actors expatiating on their roles eventually pays off with Sinead Cusack's insight into Kate's complicity with Petruchio. A trivial quote from Geri Halliwell, likening her plight to Hamlet's, is offset by the genuine irony of Laurence Olivier's son preaching the business wisdom of the Bard in corporate workshops. And astute observations occasionally displace the plot summaries, as when O'Connor points out the peculiar aptness of the US high school, with its claustrophobic codes and rituals, as a setting for updated movie remakes of Othello and The Taming of the Shrew .

But what is it that disposes Shakespeare's plays to such endless reinvention and keeps them contemporary? O'Connor is torn between the venerable view that they enshrine timeless truths of our universal condition, and the modish creed that they have always mirrored the preoccupations of the day. Both explanations, however, are as wide of the mark as Wood's belief that Shakespeare remains relevant because "he brings back life to the world we have lost" - a belief that reduces his drama to an echo from the past, and the study of it to nostalgia.

The truth is that Shakespeare's vision is still as far ahead of us as it was of his own time. In his greatest works we encounter, to quote sonnet 107, " the prophetic soul/ Of the wide world dreaming on things to come ".

Those works speak to us not only of Shakespeare's world and the world we have turned it into, but also of a world fit for his heroes and heroines, which we have yet to create.

Kiernan Ryan is professor of English, Royal Holloway, University of London.