It assumes you know a fair bit. McElreath's _Statistical Rethinking_ is a better introduction: http://xcelab.net/rm/statistical-rethinking/
It's more a good book for introduction bayesian statistic. And it's super math/stat lite.
If you really want to stick with Bayesian Statistic and need a comprehendsive stat for a foundation a better book would be: Doing Bayesian Data Analysis by John K. Kruschke.