Looks easy to follow and the design is clean. It mentions accessibility in the 'What's next?' chapter, though, while I would have hoped this would be covered as

Looks easy to follow and the design is clean. It mentions accessibility in the 'What's next?' chapter, though, while I would have hoped this would be covered as part of the material in general. For example, the section on forms suggests you use the 'for' attribute to link a label with a form element, which is great, but it wouldn't take much extra text to give a short explanation why this is helpful to many users.