The KJA books are fun, but lack the complex themes of the first few Frank Herbert books. Sort of like how Larry Niven's newer works compares to classics like Ringworld. Still fun books, but lack the rigor that made Ringworld so great.
The new books can be decent space opera, but anyone expecting to encounter anything like the beautiful and poetic prose of the originals will be very disappointed. One of the things Herbert Sr. was so good at is dialogue.. Yet his son really sucks at dialogue. Same w/ Anderson. So when you sit down to one of these books and you're thinking "Oohh Dune", and you remind yourself of all the good things that made Dune good.. the setting.. the characters.. the dialogue.. the well writen prose. The new books rely on none of that and take everything in a very different "space opera light" sort of direction.
It's like asking Michael Bay to direct the sequel to Hamlet. You might get something entertaining out of it, but fans of the original will not find the same sort of story telling in the sequel. The intended audience is just.. different.
I enjoyed reading most of the new books, but I like space opera. This isn't great space opera, and most of it isn't even good space opera. I'd call most of these books "average space opera light". Some of them were good though, and some were meh. I was buying these books a couple years after they came out (give me paperback or give me death), but then I really stopped caring. I am not really that interested to go back and find out how everything originated. I mean, it can still be interesting to read about, but most of the "let's explain how this came to be, gather round!" stuff that happens in the new books just seems forced.
It sounds like I'm saying that the new books suck, but like I said I did enjoy reading many of them. In a different way than I enjoy reading the originals. It's the same thing as you enjoying a $100 steak differently from a $5 greasy burger. Both can be tasty, just in different ways. And if you bite into a burger expecting a steak, you are going to be disappointed.
All those people who continue yellnig about these new books need to find better hobbies though. If you don't like them, don't read them *shrug*
For me, the readable ones were Dune, Messiah, and Children. I trudged through God Emperor and actually enjoyed the first 3/4 of Heretics.
The first time I read through books 4-6, my initial reaction was pretty much.. "wtf did I just read?".. I had to read the whole series again to really pick up on many of the things these books were trying to communicate to me. After the second read-through I enjoyed those books a lot more, but yeah, they are hard to follow. Some of it seems like. well.. the author took these ideas that began in Dune and spun them out of control just a tad.. but.. I believe that's because the original Dune novel has been so romanticized. It's a classic. But the themes in Dune and the themes in the overall story (books 1-6) are different. When these new themes emerge in the latter books, you end up thinking of that first book in a different way. You saw some of the hints of these themes, but now they seem to be really pulled out in a rather strange way. The more I got used to them though, the more I accepted the whole franchise as a .. different sort of thing than what it would have been if it just was that one book and nothing else. It's a different story, so you have to adapt. But the way Herbert wrote, that can be tough to do.