This book is like playing in an 18th century curiosity cabinet of the occult, secrets, and paris. Absolutely delicious. This is the book Dan Brown *wishes* he could write. Cons: Lots of "in jokes" relating to the History of Science and 16th century mysticism. A lot of the better humorous bits might elude non-historians.
Once you get into it, the plot reveals itself to be sublimely humorous. A fantastic insight into the world of self-important vanity publishing and occult studies. Cons: The first 100 pages may take a few tries to get momentum.