Have not see 2 yet but did read the books when I was younger. The first movie could have explained the beginning of the series better. The Dune series is fantastic imo. It has many deep and well thought out themes involving religion, power struggles and the control of resources. It takes place far in the future after humans had a war with intelligent systems  and what remains is a currency called spice and few groups or federation in control. In this new future humans have outlawed intelligent systems and reverted back to a feudal government and most normal folks mine spice. the control over spice is the most coveted commodity because it powers travel in this fictitious universe and also when spice is consumed by humans it is akin to drug use.