contact form 7 send custom variable to form

My use case is very simple. I have a bunch of books on my site and close to each one there is a button to pop up a "Request Info" contact form to fill.

I'd like that when the user clicks on "Request Info", the email that is sent from CF7 contains the book title too, which I then use into my wpcf7_before_send_mail function.

In other words, if there a way to use a parameter into the CF7 shortcode, so that I can then retrieve it into the before_send function?

Something like:

[contact-form-7 id=1234 title="My form" myvalue="45DC67"]

Thanks

Fabio