I read 'Bag of Bones' before 'Insomnia' and I noted a character named Ralph Roberts who informs Mike Noonan (central character in Bones)that he looks tired, perhaps he's suffering from insomnia, and Ralph Roberts knows all about that.
Much as I expected, Ralph Roberts turns out to be the hero of 'Insomnia', surely one of King's most unusual and unpredicatble novels.
King himself admits (in the forward to 'The Green Mile') that he experiences bouts of insomnia, thereby explaining the incredible insight he shows into the nature of the condition; any erstwhile insomniac will be able to relate to Ralph's experiences in the early part of 'Insomnia' in the same way that it's easier to understand the nature of a pain once you have experienced it yourself.
In some ways Ralph Roberts isn't a typical Stephen King character; for one thing he's much older than King's usual lead characters and he's neither a writer or a teacher. In some ways this is a welcome break from the pattern, although King does manage to retain other patterns which his 'constant readers' will find both pleasing and gratifying.
The story is set in Derry, surely the strangest town this side of Castle Rock and there are plently of references to other events in the history of that troubled place which should be familiar to those who have read 'It' (Mike Hanlon is still the librarian), 'Bag of Bones' or 'Dreamcatcher'. There's also a nod to the Dark Towers and intelligent suggestions concerning the layering of reality.
This is a surprising, compelling and somehow inspiring book. Ralph's insomnia is a key to far, far stranger things. It is scary in the right places, amusing in the right places and thought provoking in the right places.
Incidentally, if you do read it, and I ernestly suggest you do, it adds an extra dimension to the proceedings if you reflect afterwards that, in mythology, Atropos (one of the three fates)was considered 'The Inevitable'.