Don't believe what the back cover says, it is not a thriller. It is not necessarily a bad thing.
The story revolves around Joseph Geist, who is a failed philosophy graduate (pedantic and idealistic). At the beginning of the book, his girl friend kicks him out and breaks up with him. To top it all, he loses his graduate position at the university. His only hope comes from a classified ad posted by an old lady.
The rest of the book describes the descent of an average student, into insanity. Because the book is written using the first person, the reader feels more involved as they are not only witnessing the facts. This is the biggest selling point of this book.
On the downside, the story is slow at the best of times and is sometimes clogged with lengthy descriptions and philosophical dissertations about "light" themes such as free will, freedom, etc...
Instead of a thriller, you end up with a psychological drama. Give it a go, you could be happily surprised.