Books to Film is a very real dream of many authors. Finding those who know the industry, following them and learning from them, adopting them as mentors, is the first step to bringing your dream to reality. For me, this reality also consists of purchasing the software the big-name scriptwriters and filmmakers use and teaching myself to bring my novels to scripts. Multi-generational films/movies and their scripts can be found, and when you do find them, watch and read them through, because those are the keys to discovering why they have been popular and have become classics and successful for generations. Many of these links below will either offer insight to the industry, further details, or allow the free download of the scripts and films – you should never have to pay for them if they are in the Public Domain, yet many websites charge varying prices.
IMDb – List of PubliScreenwritings
Wikipedia – List of Films in the Public Domain