I have been looking through the documentation and trying to find something defining how to use the material-ui/styles. It is used in several examples but no section in the documentation that defines how to use it and what it capabilities are. I will continue to try and figure it out and ask for help on StackOverflow but i think this would be good to add to the documentation.
We love feedback like this one but, could you be more specific. What are you trying to do? What do you think we could add in the documentation to help?
After some additional research I found that there is a section under API for MuiThemeProvider but I did not find anything for createMuiTheme. Also under customization there is a Themes section. I like the API section and how it gives a list of Props, CSS API and Demos. It would be nice if there was one for Styles (material-ui/styles) with descriptions of the methods, parameters and classes and references to the examples. listed above. Maybe it should all be under the Style section of the documentation. That was the first place I looked when trying to find information about withStyles. Unfortunately I just started converting my application from 0.18 to 1.x beta and so I am still learning and relying on the docs so take my input with a grain of salt.
I did not find anything for createMuiTheme
@stuartsimpson We have an API section about
createMuiTheme(): https://material-ui-next.com/customization/themes/#createmuitheme-options-themewithStyles(): https://material-ui-next.com/customization/css-in-js/#withstyles-styles-options-higher-order-componentYou have a search bar for your use case:

What I think we could do to greatly improve the learning curve is building a Learn Material-UI tutorial will all the things most people will need. Next.js has been doing an excellent job with https://learnnextjs.com/. cc @kof as it can provide some inspiration.
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@stuartsimpson We have an API section about
createMuiTheme(): https://material-ui-next.com/customization/themes/#createmuitheme-options-themewithStyles(): https://material-ui-next.com/customization/css-in-js/#withstyles-styles-options-higher-order-componentYou have a search bar for your use case:

Moving forward
What I think we could do to greatly improve the learning curve is building a
Learn Material-UItutorial will all the things most people will need. Next.js has been doing an excellent job with https://learnnextjs.com/. cc @kof as it can provide some inspiration.