This is a very strange book. It's about Neil Gaiman, so it can probably afford to be. In Gaiman's house, we're informed in the introduction, "The ghost lives in the attic, and runs down the hallways and causes some house guests to run out of the house screaming in the night, although as Neil explains to visitors dragging their suitcase up to the spare room, it has never bothered him."
Being strange has been part of Gaiman's public persona ever since he set out to create one, which, on the evidence presented here, was when he was about 6.
When Hayley Campbell was 6, Gaiman stayed a while at her house. She became the guinea pig for the first of his and Dave McKean's children's picture books, The Day I Swapped My Dad For Two Goldfish; he dedicated it to her. Gaiman has an improbably large group of close friends, many of them famous and career-advancingly useful - "He was networking before networking was invented", someone comments in an early chapter here. So it's unsurprising that the person writing a major assessment of his work should turn out to be not just a lifelong fan, but a lifelong Gaiman acolyte.
Unsurprising, but unfortunate. "Part of the art of Neil Gaiman is how he traverses the terrain and flits between worlds, how he bluffed his way in and then nobody asked him to leave because he's nice and smiley and funny. Above all, they let him stay because he is an incredible storyteller with a beautiful heart and an ability to make you fall in love with anything at all."
The only good thing about this passage is that it occurs on page 19. No one encountering Campbell's dizzying lack of critical distance in later chapters can claim she didn't provide fair warning.