I rarely write reviews on Amazon but I have to say here that of the many, many books on Bayesian theory and practice that I have read over 20 years of running a consultancy which specialises in the use of these techniques, this is certainly the best as an introduction to the modern approach to Bayesian thinking in scientific problems.
After the first chapter shows why the ideas are important and where they came from, it exudes practical advice rather then unnecessary theory and continues in a carefully-considered fashion developing the complexity and background until at the end we are exposed to some pretty advanced ideas where the appropriate level of theory is then injected.
Once you have absorbed the various messages thoroughly including e.g.
- the caveats
- how to specify realistic prior knowledge
- where approximations are useful and when they are not
you will be armed to use your own expert knowledge to attack problems which - although they may at first seem to be unmanageable - will be forced to yield to the subtlety and power of probability theory via Bayes' theorem if you can collect enough data of useful quality.
I disagree strongly with one of the other reviewers here who likes everything except the section on Nested Sampling by John Skilling at the end. It may be a little different in tone but the technique is sound, important and rather easy to implement, and variations have been making waves in difficult high-dimensional problems in areas such as astrophysics for years now. It has a bright future and this is an excellent introduction to it.
If you are interested in the modern Bayesian perspective and want real gravity, rigour and depth (along with long-winded bluster, humour and personal attacks on critics) then go for Jaynes' "Probability Theory: the Logic of Science"
Probability Theory: The Logic of Science: Principles and Elementary Applications Vol 1which is the 'reference book' (though untypical in form & slightly unfinished) to support this excellent practical introduction.