Oh yeah absolutely, for prototypes you can liberally use unwrap/expect to figure out the happy path first and remove those calls later.
I haven't checked out the Rust book in quite some time, but it would be cool to make newcomers comfortable with the Result<..., Box<dyn Error>> return type early on, so they know what they have to do to make code containing "?" compile.
I haven't checked out the Rust book in quite some time, but it would be cool to make newcomers comfortable with the Result<..., Box<dyn Error>> return type early on, so they know what they have to do to make code containing "?" compile.