The Stone Trilogy Series by Graham Edwards

Jonah Lightfoot and Annie West arrive in the world of Stone. It is a spooky other-world, an endless Wall with exotic foliage crammed between the stones, air that is alive and flowing. Annie is taken over by Frey, the evil shaman of the natives, and Jonah needs the aid of the Ypoth.

This story begins with the eruption of Krakatoa, with Jonah and Annie hurled between worlds to arrive at the Wall. This is the world of Stone, called Amara. The Wall shelters entirely new and strange creatures, there are stone-age human settlements in extraordinary buildings, - and dragons.

In this final tale of Amara, the nineteenth-century historian Jonah meets a man from his own world; one Tom Coyote, who originates from the year 1980. Along with Coyote, the bizarre group of companions (including a wood-spirit inhabiting a flying boat, a once-immortal basilisk, and several others who are mostly human) ascend the world-sized monolith of Amara to find what awaits at the top, and each of them prepare to face their own demons.