The sheer magnificience of this book astounds even the most intellectual of minds. No it is not a normal book by most conventions, there is no true action to speak of, and this book mainly centers around the dialogue between Leto and those around him. But it is a most important book in that we see what it is to be a messiah and more importantly what it is to be human and how one can never truly be released from that bond.
Leto's struggle is within himself and this is shown through his journals and his anger with humanity. Leto is the ultimate teacher and all of mankind are his students and he sees the patterns mankind holds intrinsically. Each of the characters is well developed with Leto being the one of the greatest of all time.
This is not simply a book by an incredibly intelligent man, but Herbert's warning to mankind about becoming entrapped in one's own patterns and how it takes an outside observer to chnage those patterns.