The Witness for the Dead

This is definitely a book. It has pages, some characters, a plot, it even has some dialogue. So it passes the “is it a book” test. Otherwise...

This book is kinda like if Miles from Lost got a spin-off, but didn't have any snark. Like, Miles is cool, but you're not watching Lost for Miles, and without the snark, you're just kinda left with an undeveloped character who can talk to dead people.