Beatrice and Claudia end up agreeing that the leading candidate is de Vere, with Ignotus second and Stratford a very distant third. Beatrice’s entries lead to a final probability of 10−13 (one chance in ten million million) that Shakespeare was the gentleman from Stratford-upon-Avon. Claudia’s entries lead to an even smaller probability.
I don't think I want to use this book to try to learn how to produce to well-calibrated probability estimates.
Why not? The first time I cranked through an example of this nature, it was -extremely- educational. If you're beyond this level, that's fine, but in that case your message doesn't contribute anything to the conversation.
Disclaimer: I have not read this book. I'm posting it in the expectation that others may enjoy it as much as I'm sure I would if I had time to read it myself.
This looks interesting as an extended worked example of Bayesian reasoning (the "scientific approach" of the title).
Edited to add:
There are many signs in the above block of text that this book is not up to Lesswrong standards. As gwern suggests, reading it should be done with an adversarial attitude.
I propose some more useful goals than finding someone for whom we can cheer loudly as a properly qualified member of our tribe: find worked examples that let you practice your art; find structured activities that will actually lead you to practice your art; try to critically assess arguments that use the tools we think powerful, then discuss your criticism on a forum like Lesswrong where your errors are likely to be discovered and your insights are likely to be rewarded (with tasty karma).