It's an unsorted collection of web-oriented tips and tricks. The UX entries almost exclusively focus on improving user experience around conversion points, and are not generally applicable.

Hints on spacing, layout, text formatting, etc. are largely trivial, but there's probably value in verbalizing them for people who are just starting up. However, it would've probably been better - for a book - to "group logically related elements" together instead of having them scattered around the place.

There are some less obvious items that pick up on right things, but what prompted me to comment is that many "hints" don't apply universally and are highly context-specific. There also some that are way off.

  ---

From the "way off" department -

> Make links look like links

In general, yes, but the Twitter example given shows that the OP doesn't grok why it's done that way. UI elements have UX priorities. If you give prominence to all actionable elements regardless of their importance, you will end up with a circus. And if you tuck them away behind an expander or a burger, then you hinder the usability. So the common "trick" is to de-emphasize secondary elements, yet keep them discoverable. Just like Twitter people did it here.

> Consider removing confirmation modals

This makes no material difference - it's either user mindlessly clicking on "Confirm" or being retrained to mindlessly click on "Restore". Potato-potata, just looks different. Besides there's also an in-place modal-less confirmations.

> Submitting verification code

Oh, don't you dare. Stripe does this (auto-submits the form on the last digit entry) and it is exceptionally annoying. People make typos, including the last digit. Allow for that.

  ---

From the "don't apply universally" department - pretty much everything that's form related:

> Don't hide form tips

> Require fewer fields

> Use labels instead of relying on placeholders

> Use reasonable width of inputs, the splitting date into three fields part

> Don't use complex forms in modals

This squarely depends on the form. It's one thing if I am trying to convert a visitor into a user and another if I am trying to make a back-office data entry person happy.

  ---

All in all, it's a solid domain name, with a good potential; the list itself is OK if a bit random and in a need of some clarification.

But the PDF is neither a book nor is it about UI per se.