I can't recall Godmakers now, but it is in my library somewhere. Will have to dig it out sometime!
One that is extremely hard going is Destination: Void. Good concept - the skeleton crew of a sleeper spaceship attempting to activate a consciousness that will succesfully steer them to their destination. Problem is the 'minds' keep going mad. Unfortunately it gets very bogged down in the technicalities.
The Jesus Incident is a semi-sequel to the above and is more 'Dune-like' in style. It is Herbert's attempt to create another world, this time a watery one, on the same scale as Arrakis. It doesn't come close to those heights, but its definately not a bad read. There are two further follow ups which I think are called The Ascension Factor and The Lazarus Effect . The three of them were co-written with Bill Ransom, but the last one was penned almost entirely by Ransom as Herbert passed away having got no further than the outline.
Two more good Herbert reads:
The Dosadi Experiment and Whipping Star which both feature the author's favourite charachter, Saboteur Extraordinary Jorj X. McKie.