Frankly its just a very violent adventure, with enough links to the past 3 books to be worth reading to see a very small progression in the overall series. If there's no further books soon it's not really worth it.
Now the signed part is maybe autopen, I suspect it's simply printed. I've always considered it a cheat unless the author has personally signed the individual book with a pen. There again what do you expect with a large print run 'limited edition', and it's
an amusing and series specific one.