From the other side
There is a demon in it. How dark does it actually get?
A straight answer about how frightening The Demon and The doG is, what is in it, and the age it stops being suitable in either direction.
This is the first question most parents ask and it deserves a straight answer rather than reassurance.
The Demon and The doG is played for adventure and for laughs, not for horror. The demon is the protagonist and he is much more harassed than he is menacing. There is no gore. There is no possession. Nothing in it is designed to be frightening at bedtime, and the cover, with its bats and its full moon, is broadly as dark as the contents get.
What is actually in it
A demon with a job. A dog who is more than a match for him. A plot he uncovers and does not understand. An unlikely friendship with somebody who likes jokes. Gross out humour, of the kind that a nine year old finds much funnier than their parent does.
The publisher's stated range is seven to twelve, grades two to six.
Where a parent might reasonably say no
If your family's line is that demons are not a subject for entertainment at all, this book crosses it on page one and no amount of context changes that. That is a coherent position and it is better served by knowing now.
If your reader is genuinely frightened by the idea of the underworld rather than by depictions of it, the cover alone may be enough to put them off, and an unread book on a shelf helps nobody.
If you want to know exactly how dark it gets before handing it over, ask Bryant. He answers that question himself and he would rather answer it than sell you the wrong book.
The cover does more frightening than the book does
Worth saying separately, because it catches people out. The cover has bats crossing a full moon over a dark village and the word DEMON across the top in large letters. It is the most gothic object in the entire package.
Children generally find this thrilling rather than alarming, which is the point of a cover at this age. Adults buying it sight unseen for somebody else's child occasionally do not, and it is better to know that before it is unwrapped at a birthday party in front of the parents.
What it is not
It is not horror, it is not spiritual warfare instruction, and it is not a book about resisting temptation dressed as a story. There is no scene designed to make a child afraid of anything, and nothing in it teaches a child that something is coming for them at night.
If anything the effect runs the other way. A demon you have spent eighty pages laughing at is a demon that has lost most of its power to frighten, which is roughly what Lewis said he was doing when people asked him the same question about Screwtape.
The other direction
There is also a too old. A confident thirteen year old reader will finish this in an afternoon and find it slight, because it is eighty three pages written for someone younger. The A.I. and The Alien, at a hundred and seventy one pages and a stated range of ten to twelve, is the one to reach for then.
This is one part of faith fiction told from the other side, the idea behind both books and the podcast.