Restraint and economy have never been hallmarks of Robin Jarvis’s style. You get the flavour from his choice of names. The tiny werlings who dwell in Hagwood include Gamaliel Tumpin, our vulnerable hero, Finnen Lufkin and Tollychook Umbelnapper. Their shape-shifting skills are useless against Krakkwhipp, Naggatash and the rest of the thorn ogres, “tortured shrubs of briar and bramble”.

Jarvis’s adventure is punctuated by grand set pieces: the encounter with Frighty Aggie, the night ride of the Unseelie Court and the death of Gofannan, the wandering smith.

As each episode develops, his prose climbs into a more frenetic gear. Adjectives cluster on the backs of their nouns, sentences invert to lend heroic grandeur (“Great was their number...”) and malevolence drips from his alliterative pen. And he knows well how to recruit a young reader’s anxious sympathy for the diminutive, clumsy Gamaliel, beset by evil.

Tolkien employed the same devices, borrowed from Anglo-Saxon and Norse epics. His stories, and Jarvis’s own fine Wyrd Museum trilogy, draw upon older mythologies to imply that in these dangerous worlds there are other tales to be told, other times to be travelled. Thorn Ogres does not have that depth, but it will nevertheless excite those who love to ride a bucking, twisting plot and relish desperate courage pitted against sadistic powers, where even the Great Grand Wergle Master can commit the basest treachery, and get his nose bitten off as his reward. In the final pages, we are promised more of the werlings’ struggle with the icy queen, The High Lady Rhiannon Rigantona.

Susan Cooper offers older readers a different kind of excitement. King of Shadows is a time-slip - or rather a time-swap - novel. In 1999, young Nat Field is one of a group of boy actors gathered in Cambridge, Massachusetts, rehearsing A Midsummer Night’s Dream under their hard-driving director. The company is due to perform at the Globe in London, but before the run starts, Nat is hospitalised with a mysterious illness and wakes up to find himself a member of The Lord Chamberlain’s Men in 1599.

Here he stays for much of the story, working with Shakespeare, Richard Burbage, Robert Armin and the rest. Nat’s performance as Puck delights the Elizabethan Globe audience, which includes the incognito Queen herself.

His return to the present day is equally sudden. As the kaleidoscope settles, he sees the pattern. The Nathaniel Field of Shakespeare’s time took Nat’s place in the 20th-century hospital to be cured of bubonic plague; if he had stayed in 1599, he would almost certainly have infected Shakespeare, and where would Hamlet and Lear have been then? Through his tenderly subtle relationship with Shakespeare, Nat has come closer to accepting the death of his poet father. And who has orchestrated this time exchange?

Susan Cooper has to work very hard to pull all this off. She cannot assume her readers’ knowledge of the Globe, of Elizabethan London, or the text of The Dream, essential to her plot.

The right reader will find fascination, and information, in the historical and theatrical ambience. The late Geoffrey Trease loved this fictional territory too, and his kind of passion, which Susan Cooper clearly shares, is not around much at present in children’s books.

Geoff Fox.