I don't know the name of it. It was a book of black and white sketch like drawings of different pretend monsters, but not cryptids. They may have been monsters that looked like household objects, one of them was possibly a coat hanger type thing. Each page had a description of a monster and then a black and white picture/sketch of them. It was definitely published before 2015 and was meant for either children or preteens.
I’m not familiar with the story, but it seems like it could be :
A Manual of House Monsters, Marijanovic, Stanislav
https://www.abebooks.com/book-search/author/marijanovic-stanislav/
This isn’t it but thank you for trying!
I wondered if it might have been *Flanimals* by Ricky Gervais, but the illustrations for that are in colour.
There was a similar book in my library that has since been discarded. I thought it was called The Book of Monsters, or possibly just Monsters. I don’t remember the author, but I know the name started with either O or P…and I’m leaning towards O. Ostereen? Osteen? Something like that. There were actually two books, with similar premises and titles. Good luck!