I own and read both books. Mark Pilgrim has a more straightforward approach and his book seems to be more about getting things done. I usually use it to get ideas whilst working on an implementation or use it as a reference.

Whereas Introducing HTML5 is a great read and gives a lot of background information about certain design choices. It also covers almost everything. It's my favourite HTML5 book.

As for one last comparison, I think a newcomer would find it harder to follow Dive Into HTML5 but you get sucked into Introducing HTML5 really fast. In a couple of chapters, it gives you enough to start playing with this new thing you've learnt.

I'm not going to judge a book by its cover. All I can see here is list of chapters and some links to related projects. Unlike Dive into HTML5, there is no free online html version of book here. May be someone who have read it can tell it better.

However, I found these resources on html5 to be very informative.

http://slides.html5rocks.com http://studio.html5rocks.com/