Last year I was researching stochastic methods and Wikipedia was a great help in this regards. During this time, learnt about a neat feature of Wikipedia.
Wikipedia offered a service using which one can curate an ebook of the selected wikipedia topics and then export the book as PDF or ePub.
Here’s my attempt. A very short ebook on stochastic methods. Download it from here. The table of content as shown in the image. And while you are at it, you might want to read this presentation on Introduction of Spectral Methods!!