There is a large number of html format books on bookdown.org, mostly related to Data Science and R, lots of Bayesian too. There are some more theoretical math b

There is a large number of html format books on bookdown.org, mostly related to Data Science and R, lots of Bayesian too. There are some more theoretical math books there, one of which I found to be very well written: Theory of Distributions by Peter K. Dunn