All right - I'm into the Berkeley chapter, titled: Clearing Up The Mess.
Color me skeptical that the mess will really be cleared up! I really wanted to finish last night, but I couldn't stay awake. I am 40 chapters from the "end," and then there are 44 pages of appendices where the various possible solutions are revealed to us.
I am massively enjoying this extraordinarily quirky little mystery and I hope that my sense that the authors are having a blast is accurate because it certainly feels that way to me. My copy has the tag line "The Most Unusual Mystery Ever Written," and I would say that, while hyperbolic, there's a fair argument to be made that it's accurate!