From the wiki page, there are many useful FAQ/ guides/ docs. Specifically, there is a link to a decent guide:
http://adamantine.me/index.php/2015/11/18/umatrix-desperatel...
edit: using both is redundant
In fairness to gorhill it's a couple of years since I last looked at uMatrix so it may be much improved.
uMatrix handles network stuff (blocking css, js, media, etc).
uBlock also handles network stuff, but the difference is that uBlock can also block specific elements on the page, eg, divs by id or class.
If you block all JS and CSS with umatrix, you can still read articles by pressing the "reader view" button in Firefox.
https://addons.mozilla.org/en-US/firefox/addon/styl-us/
https://chrome.google.com/webstore/detail/stylus/clngdbkpkpe...