Jan Mark visits the lost worlds of Dinotopia and Fumoria. Dinotopia and The Three Counties of Fumoria are reminiscent of those huge and complex model railway layouts ostensibly bought for sons and played with by fathers. Layout matters: both Gurney and Warren have a passion for maps, charts, plans, labyrinths, systems, alphabets, data; each is in thrall to the notion of a lost world, a Vernesque lost world, in the case of Dinotopia. The whole enterprise - I use the word advisedly: Dinotopia is a trademark already - is set firmly in the mid-19th century, an island continent that can be located only by accident, where mankind and dinosaurs exist in peace and harmony.

The peace-and-harmony bit is actually something of a hindrance to narrative development since in this demi-paradise, not even man is vile. At most, man is misguided.

Consequently nothing much happens and what passes for a story is rather limp and disjointed, with lengthy digressions. This scarcely matters; Gurney is primarily an artist and a gifted pasticheur; the machines nod to Robocop, the buildings come courtesy of Gaud! (especially the charming pod houses); one whole section could be the work of late Victorian academicians. Overall it is a curious hybrid - a coffee-table picture book. Nevertheless it is clearly a labour of love, however many giga-dollars are riding on it, radiating good humour and gentleness. Not a drop of blood is spilt throughout; even Tyrannosaurus Rex is a reasonable chap so long as you do not tread on his corns.

River Quest and Windchaser are two dullish, slipshod spinoffs. They purport to be the work of different people, in which case they have been edited by the same computer, one obsessed with 13-year-olds. The heroine of River Quest has her age mentioned half a dozen times. The hero of Windchaser almost drops out of the story when he turns 14, leaving the field clear for his pal Hugh who speaks “with a thick, lower class London accent”. The American author’s attempts to render this - indeed, to remember it - are periodically hilarious.

Apart from genuine Gurney cover designs the books are unillustrated, and being assembled by authors with indifferent powers of description, lean heavily on a familiarity with the original art work, available only in the aforementioned pricey tome. Which leaves one with the dark suspicion that this may be the object of the exercise.

Caleb Beldragon’s Chronicles is a more modest undertaking in execution, although packaged as an interactive quest which, if you solve The Riddle, will win you an “enchanting tower in a rural location”. However, the Chronicles are just what they claim to be, an illustrated guide to the Three Counties inhabited by the Ids, the Urgs and the Gibblins. Caleb himself is a Gibblin, so the accounts tend to be weighted in their favour.

In any case, they are not unlike us. They have a similar history, mythology, astrology and folklore. They live under a repressive regime ruled by Lord Mulciber the Deathless, in towns called Scrotty Codfield, Little Snogging, Ratley Bagford and Warty Orton.

Warren’s is a more raucous spirit than Gurney’s; his own particular homage is to Breughel and his jokes, both verbal and visual, are cheerfully vulgar.

The voices of Tolkein and Peake breathe o’er Fumoria. It is all much closer to home than Dinotopia, but, once again, this is a private world gone public.