Thanks. I'd heard that before about the 2nd and 3rd books. Didn't know there was a 4th.
It's been a long time, but I remember really liking all 3 and I have the 4th in my TBR pile which I will eventually read. And just seeing that he has written a 5th, yep, I'll probably read that too.
I enjoyed 2 and 3 as well. Haven't read the one by the new author, but I will get around to it eventually.
One of the things that I found very amusing in book 2 was Lisbeth's musings on Fermat's Last Theorem. My book club didn't get why I found it funny, though. Not to literally spoil anything, but she keeps coming back to it at not so appropriate times in the action.